iknow-lab/mysql_manual_8_4_en · Datasets at Hugging Face

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https://dev.mysql.com/doc/refman/8.4/en/performance-schema-cond-instances-table.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="performance-schema-cond-instances-table"> </a> 29.12.3.1 The cond_instances Table </h4> </div> </div> </div> <a class="indexterm" name="idm46045073599312"> </a> <a class="indexterm" name="idm46045073597824"> </a> <p> The <a class="link" href="performance-schema-cond-instances-table.html" title="29.12.3.1 The cond_instances Table"> <code class="literal"> cond_instances </code> </a> table lists all the conditions seen by the Performance Schema while the server executes. A condition is a synchronization mechanism used in the code to signal that a specific event has happened, so that a thread waiting for this condition can resume work. </p> <p> When a thread is waiting for something to happen, the condition name is an indication of what the thread is waiting for, but there is no immediate way to tell which other thread, or threads, causes the condition to happen. </p> <p> The <a class="link" href="performance-schema-cond-instances-table.html" title="29.12.3.1 The cond_instances Table"> <code class="literal"> cond_instances </code> </a> table has these columns: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> NAME </code> </p> <p> The instrument name associated with the condition. </p> </li> <li class="listitem"> <p> <code class="literal"> OBJECT_INSTANCE_BEGIN </code> </p> <p> The address in memory of the instrumented condition. </p> </li> </ul> </div> <p> The <a class="link" href="performance-schema-cond-instances-table.html" title="29.12.3.1 The cond_instances Table"> <code class="literal"> cond_instances </code> </a> table has these indexes: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> Primary key on ( <code class="literal"> OBJECT_INSTANCE_BEGIN </code> ) </p> </li> <li class="listitem"> <p> Index on ( <code class="literal"> NAME </code> ) </p> </li> </ul> </div> <p> <a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement"> <code class="literal"> TRUNCATE TABLE </code> </a> is not permitted for the <a class="link" href="performance-schema-cond-instances-table.html" title="29.12.3.1 The cond_instances Table"> <code class="literal"> cond_instances </code> </a> table. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/innodb-file-per-table-tablespaces.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="innodb-file-per-table-tablespaces"> </a> 17.6.3.2 File-Per-Table Tablespaces </h4> </div> </div> </div> <a class="indexterm" name="idm46045165503168"> </a> <a class="indexterm" name="idm46045165501664"> </a> <p> A file-per-table tablespace contains data and indexes for a single <code class="literal"> InnoDB </code> table, and is stored on the file system in a single data file. </p> <p> File-per-table tablespace characteristics are described under the following topics in this section: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <a class="xref" href="innodb-file-per-table-tablespaces.html#innodb-file-per-table-configuration" title="File-Per-Table Tablespace Configuration"> File-Per-Table Tablespace Configuration </a> </p> </li> <li class="listitem"> <p> <a class="xref" href="innodb-file-per-table-tablespaces.html#innodb-file-per-table-data-files" title="File-Per-Table Tablespace Data Files"> File-Per-Table Tablespace Data Files </a> </p> </li> <li class="listitem"> <p> <a class="xref" href="innodb-file-per-table-tablespaces.html#innodb-file-per-table-advantages" title="File-Per-Table Tablespace Advantages"> File-Per-Table Tablespace Advantages </a> </p> </li> <li class="listitem"> <p> <a class="xref" href="innodb-file-per-table-tablespaces.html#innodb-file-per-table-disadvantages" title="File-Per-Table Tablespace Disadvantages"> File-Per-Table Tablespace Disadvantages </a> </p> </li> </ul> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="innodb-file-per-table-configuration"> </a> File-Per-Table Tablespace Configuration </h5> </div> </div> </div> <p> <code class="literal"> InnoDB </code> creates tables in file-per-table tablespaces by default. This behavior is controlled by the <a class="link" href="innodb-parameters.html#sysvar_innodb_file_per_table"> <code class="literal"> innodb_file_per_table </code> </a> variable. Disabling <a class="link" href="innodb-parameters.html#sysvar_innodb_file_per_table"> <code class="literal"> innodb_file_per_table </code> </a> causes <code class="literal"> InnoDB </code> to create tables in the system tablespace. </p> <p> An <a class="link" href="innodb-parameters.html#sysvar_innodb_file_per_table"> <code class="literal"> innodb_file_per_table </code> </a> setting can be specified in an option file or configured at runtime using a <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment"> <code class="literal"> SET GLOBAL </code> </a> statement. Changing the setting at runtime requires privileges sufficient to set global system variables. See <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges"> Section 7.1.9.1, “System Variable Privileges” </a> . </p> <p> Option file: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa89140588"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span> <span class="token constant">innodb_file_per_table</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span></code></pre> </div> <p> Using <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment"> <code class="literal"> SET GLOBAL </code> </a> at runtime: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa10292868"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_file_per_table<span class="token operator">=</span><span class="token keyword">ON</span><span class="token punctuation">;</span></code></pre> </div> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="innodb-file-per-table-data-files"> </a> File-Per-Table Tablespace Data Files </h5> </div> </div> </div> <p> A file-per-table tablespace is created in an <code class="filename"> .ibd </code> data file in a schema directory under the MySQL data directory. The <code class="filename"> .ibd </code> file is named for the table ( <code class="filename"> <em class="replaceable"> <code> table_name </code> </em> .ibd </code> ). For example, the data file for table <code class="literal"> test.t1 </code> is created in the <code class="filename"> test </code> directory under the MySQL data directory: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34238097"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">USE</span> test<span class="token punctuation">;</span> <span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span> <span class="token prompt"> -></span> id <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token keyword">AUTO_INCREMENT</span><span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token keyword">name</span> <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token punctuation">)</span> <span class="token prompt"> -></span> <span class="token punctuation">)</span> <span class="token keyword">ENGINE</span> <span class="token operator">=</span> InnoDB<span class="token punctuation">;</span> <span class="token prompt">mysql></span> <span class="token keyword">EXIT</span><span class="token punctuation">;</span></code></pre> </div> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa73359084"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">cd</span> /<em class="replaceable">path</em>/<em class="replaceable">to</em>/<em class="replaceable">mysql</em>/data/test <span class="token prompt">$> </span><span class="token command">ls</span> t1<span class="token punctuation">.</span>ibd</code></pre> </div> <p> You can use the <code class="literal"> DATA DIRECTORY </code> clause of the <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement"> <code class="literal"> CREATE TABLE </code> </a> statement to implicitly create a file-per-table tablespace data file outside of the data directory. For more information, see <a class="xref" href="innodb-create-table-external.html" title="17.6.1.2 Creating Tables Externally"> Section 17.6.1.2, “Creating Tables Externally” </a> . </p> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="innodb-file-per-table-advantages"> </a> File-Per-Table Tablespace Advantages </h5> </div> </div> </div> <p> File-per-table tablespaces have the following advantages over shared tablespaces such as the system tablespace or general tablespaces. </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> Disk space is returned to the operating system after truncating or dropping a table created in a file-per-table tablespace. Truncating or dropping a table stored in a shared tablespace creates free space within the shared tablespace data file, which can only be used for <code class="literal"> InnoDB </code> data. In other words, a shared tablespace data file does not shrink in size after a table is truncated or dropped. </p> </li> <li class="listitem"> <p> A table-copying <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> operation on a table that resides in a shared tablespace can increase the amount of disk space occupied by the tablespace. Such operations may require as much additional space as the data in the table plus indexes. This space is not released back to the operating system as it is for file-per-table tablespaces. </p> </li> <li class="listitem"> <p> <a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement"> <code class="literal"> TRUNCATE TABLE </code> </a> performance is better when executed on tables that reside in file-per-table tablespaces. </p> </li> <li class="listitem"> <p> File-per-table tablespace data files can be created on separate storage devices for I/O optimization, space management, or backup purposes. See <a class="xref" href="innodb-create-table-external.html" title="17.6.1.2 Creating Tables Externally"> Section 17.6.1.2, “Creating Tables Externally” </a> . </p> </li> <li class="listitem"> <p> You can import a table that resides in file-per-table tablespace from another MySQL instance. See <a class="xref" href="innodb-table-import.html" title="17.6.1.3 Importing InnoDB Tables"> Section 17.6.1.3, “Importing InnoDB Tables” </a> . </p> </li> <li class="listitem"> <p> Tables created in file-per-table tablespaces support features associated with <code class="literal"> DYNAMIC </code> and <code class="literal"> COMPRESSED </code> row formats, which are not supported by the system tablespace. See <a class="xref" href="innodb-row-format.html" title="17.10 InnoDB Row Formats"> Section 17.10, “InnoDB Row Formats” </a> . </p> </li> <li class="listitem"> <p> Tables stored in individual tablespace data files can save time and improve chances for a successful recovery when data corruption occurs, when backups or binary logs are unavailable, or when the MySQL server instance cannot be restarted. </p> </li> <li class="listitem"> <p> Tables created in file-per-table tablespaces can be backed up or restored quickly using MySQL Enterprise Backup, without interrupting the use of other <code class="literal"> InnoDB </code> tables. This is beneficial for tables on varying backup schedules or that require backup less frequently. See <a class="ulink" href="/doc/mysql-enterprise-backup/8.4/en/partial.html" target="_top"> Making a Partial Backup </a> for details. </p> </li> <li class="listitem"> <p> File-per-table tablespaces permit monitoring table size on the file system by monitoring the size of the tablespace data file. </p> </li> <li class="listitem"> <p> Common Linux file systems do not permit concurrent writes to a single file such as a shared tablespace data file when <a class="link" href="innodb-parameters.html#sysvar_innodb_flush_method"> <code class="literal"> innodb_flush_method </code> </a> is set to <code class="literal"> O_DIRECT </code> . As a result, there are possible performance improvements when using file-per-table tablespaces in conjunction with this setting. </p> </li> <li class="listitem"> <p> Tables in a shared tablespace are limited in size by the 64TB tablespace size limit. By comparison, each file-per-table tablespace has a 64TB size limit, which provides plenty of room for individual tables to grow in size. </p> </li> </ul> </div> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="innodb-file-per-table-disadvantages"> </a> File-Per-Table Tablespace Disadvantages </h5> </div> </div> </div> <p> File-per-table tablespaces have the following disadvantages compared to shared tablespaces such as the system tablespace or general tablespaces. </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> With file-per-table tablespaces, each table may have unused space that can only be utilized by rows of the same table, which can lead to wasted space if not properly managed. </p> </li> <li class="listitem"> <p> <code class="literal"> fsync </code> operations are performed on multiple file-per-table data files instead of a single shared tablespace data file. Because <code class="literal"> fsync </code> operations are per file, write operations for multiple tables cannot be combined, which can result in a higher total number of <code class="literal"> fsync </code> operations. </p> </li> <li class="listitem"> <p> <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server"> <span class="command"> <strong> mysqld </strong> </span> </a> must keep an open file handle for each file-per-table tablespace, which may impact performance if you have numerous tables in file-per-table tablespaces. </p> </li> <li class="listitem"> <p> More file descriptors are required when each table has its own data file. </p> </li> <li class="listitem"> <p> There is potential for more fragmentation, which can impede <a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement"> <code class="literal"> DROP TABLE </code> </a> and table scan performance. However, if fragmentation is managed, file-per-table tablespaces can improve performance for these operations. </p> </li> <li class="listitem"> <p> The buffer pool is scanned when dropping a table that resides in a file-per-table tablespace, which can take several seconds for large buffer pools. The scan is performed with a broad internal lock, which may delay other operations. </p> </li> <li class="listitem"> <p> The <a class="link" href="innodb-parameters.html#sysvar_innodb_autoextend_increment"> <code class="literal"> innodb_autoextend_increment </code> </a> variable, which defines the increment size for extending the size of an auto-extending shared tablespace file when it becomes full, does not apply to file-per-table tablespace files, which are auto-extending regardless of the <a class="link" href="innodb-parameters.html#sysvar_innodb_autoextend_increment"> <code class="literal"> innodb_autoextend_increment </code> </a> setting. Initial file-per-table tablespace extensions are by small amounts, after which extensions occur in increments of 4MB. </p> </li> </ul> </div> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/do.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="do"> </a> 15.2.3 DO Statement </h3> </div> </div> </div> <a class="indexterm" name="idm46045182811488"> </a> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa67072904"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">DO</span> <em class="replaceable">expr</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">expr</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre> </div> <p> <a class="link" href="do.html" title="15.2.3 DO Statement"> <code class="literal"> DO </code> </a> executes the expressions but does not return any results. In most respects, <a class="link" href="do.html" title="15.2.3 DO Statement"> <code class="literal"> DO </code> </a> is shorthand for <code class="literal"> SELECT <em class="replaceable"> <code> expr </code> </em> , ... </code> , but has the advantage that it is slightly faster when you do not care about the result. </p> <p> <a class="link" href="do.html" title="15.2.3 DO Statement"> <code class="literal"> DO </code> </a> is useful primarily with functions that have side effects, such as <a class="link" href="locking-functions.html#function_release-lock"> <code class="literal"> RELEASE_LOCK() </code> </a> . </p> <p> Example: This <a class="link" href="select.html" title="15.2.13 SELECT Statement"> <code class="literal"> SELECT </code> </a> statement pauses, but also produces a result set: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47891606"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SLEEP</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> SLEEP(5) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 0 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (5.02 sec)</span></code></pre> </div> <p> <a class="link" href="do.html" title="15.2.3 DO Statement"> <code class="literal"> DO </code> </a> , on the other hand, pauses without producing a result set.: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa21997559"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">DO</span> <span class="token function">SLEEP</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (4.99 sec)</span></code></pre> </div> <p> This could be useful, for example in a stored function or trigger, which prohibit statements that produce result sets. </p> <p> <a class="link" href="do.html" title="15.2.3 DO Statement"> <code class="literal"> DO </code> </a> only executes expressions. It cannot be used in all cases where <code class="literal"> SELECT </code> can be used. For example, <code class="literal"> DO id FROM t1 </code> is invalid because it references a table. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/index-page-merge-threshold.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="index-page-merge-threshold"> </a> 17.8.11 Configuring the Merge Threshold for Index Pages </h3> </div> </div> </div> <p> You can configure the <code class="literal"> MERGE_THRESHOLD </code> value for index pages. If the <span class="quote"> “ <span class="quote"> page-full </span> ” </span> percentage for an index page falls below the <code class="literal"> MERGE_THRESHOLD </code> value when a row is deleted or when a row is shortened by an <a class="link" href="update.html" title="15.2.17 UPDATE Statement"> <code class="literal"> UPDATE </code> </a> operation, <code class="literal"> InnoDB </code> attempts to merge the index page with a neighboring index page. The default <code class="literal"> MERGE_THRESHOLD </code> value is 50, which is the previously hardcoded value. The minimum <code class="literal"> MERGE_THRESHOLD </code> value is 1 and the maximum value is 50. </p> <p> When the <span class="quote"> “ <span class="quote"> page-full </span> ” </span> percentage for an index page falls below 50%, which is the default <code class="literal"> MERGE_THRESHOLD </code> setting, <code class="literal"> InnoDB </code> attempts to merge the index page with a neighboring page. If both pages are close to 50% full, a page split can occur soon after the pages are merged. If this merge-split behavior occurs frequently, it can have an adverse affect on performance. To avoid frequent merge-splits, you can lower the <code class="literal"> MERGE_THRESHOLD </code> value so that <code class="literal"> InnoDB </code> attempts page merges at a lower <span class="quote"> “ <span class="quote"> page-full </span> ” </span> percentage. Merging pages at a lower page-full percentage leaves more room in index pages and helps reduce merge-split behavior. </p> <p> The <code class="literal"> MERGE_THRESHOLD </code> for index pages can be defined for a table or for individual indexes. A <code class="literal"> MERGE_THRESHOLD </code> value defined for an individual index takes priority over a <code class="literal"> MERGE_THRESHOLD </code> value defined for the table. If undefined, the <code class="literal"> MERGE_THRESHOLD </code> value defaults to 50. </p> <h4> <a name="idm46045161921136"> </a> Setting MERGE_THRESHOLD for a Table </h4> <p> You can set the <code class="literal"> MERGE_THRESHOLD </code> value for a table using the <em class="replaceable"> <code> table_option </code> </em> <code class="literal"> COMMENT </code> clause of the <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement"> <code class="literal"> CREATE TABLE </code> </a> statement. For example: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44551888"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span> id <span class="token datatype">INT</span><span class="token punctuation">,</span> <span class="token keyword">KEY</span> id_index <span class="token punctuation">(</span>id<span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token keyword">COMMENT</span><span class="token operator">=</span><span class="token string">'MERGE_THRESHOLD=45'</span><span class="token punctuation">;</span></code></pre> </div> <p> You can also set the <code class="literal"> MERGE_THRESHOLD </code> value for an existing table using the <em class="replaceable"> <code> table_option </code> </em> <code class="literal"> COMMENT </code> clause with <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> : </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa77746136"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span> id <span class="token datatype">INT</span><span class="token punctuation">,</span> <span class="token keyword">KEY</span> id_index <span class="token punctuation">(</span>id<span class="token punctuation">)</span> <span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">COMMENT</span><span class="token operator">=</span><span class="token string">'MERGE_THRESHOLD=40'</span><span class="token punctuation">;</span></code></pre> </div> <h4> <a name="idm46045161911328"> </a> Setting MERGE_THRESHOLD for Individual Indexes </h4> <p> To set the <code class="literal"> MERGE_THRESHOLD </code> value for an individual index, you can use the <em class="replaceable"> <code> index_option </code> </em> <code class="literal"> COMMENT </code> clause with <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement"> <code class="literal"> CREATE TABLE </code> </a> , <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> , or <a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement"> <code class="literal"> CREATE INDEX </code> </a> , as shown in the following examples: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> Setting <code class="literal"> MERGE_THRESHOLD </code> for an individual index using <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement"> <code class="literal"> CREATE TABLE </code> </a> : </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60266295"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span> id <span class="token datatype">INT</span><span class="token punctuation">,</span> <span class="token keyword">KEY</span> id_index <span class="token punctuation">(</span>id<span class="token punctuation">)</span> <span class="token keyword">COMMENT</span> <span class="token string">'MERGE_THRESHOLD=40'</span> <span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre> </div> </li> <li class="listitem"> <p> Setting <code class="literal"> MERGE_THRESHOLD </code> for an individual index using <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> : </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa31890012"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span> id <span class="token datatype">INT</span><span class="token punctuation">,</span> <span class="token keyword">KEY</span> id_index <span class="token punctuation">(</span>id<span class="token punctuation">)</span> <span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">DROP</span> <span class="token keyword">KEY</span> id_index<span class="token punctuation">;</span> <span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">ADD</span> <span class="token keyword">KEY</span> id_index <span class="token punctuation">(</span>id<span class="token punctuation">)</span> <span class="token keyword">COMMENT</span> <span class="token string">'MERGE_THRESHOLD=40'</span><span class="token punctuation">;</span></code></pre> </div> </li> <li class="listitem"> <p> Setting <code class="literal"> MERGE_THRESHOLD </code> for an individual index using <a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement"> <code class="literal"> CREATE INDEX </code> </a> : </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa92262354"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span>id <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">CREATE</span> <span class="token keyword">INDEX</span> id_index <span class="token keyword">ON</span> t1 <span class="token punctuation">(</span>id<span class="token punctuation">)</span> <span class="token keyword">COMMENT</span> <span class="token string">'MERGE_THRESHOLD=40'</span><span class="token punctuation">;</span></code></pre> </div> </li> </ul> </div> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> You cannot modify the <code class="literal"> MERGE_THRESHOLD </code> value at the index level for <code class="literal"> GEN_CLUST_INDEX </code> , which is the clustered index created by <code class="literal"> InnoDB </code> when an <code class="literal"> InnoDB </code> table is created without a primary key or unique key index. You can only modify the <code class="literal"> MERGE_THRESHOLD </code> value for <code class="literal"> GEN_CLUST_INDEX </code> by setting <code class="literal"> MERGE_THRESHOLD </code> for the table. </p> </div> <h4> <a name="idm46045161886736"> </a> Querying the MERGE_THRESHOLD Value for an Index </h4> <p> The current <code class="literal"> MERGE_THRESHOLD </code> value for an index can be obtained by querying the <a class="link" href="information-schema-innodb-indexes-table.html" title="28.4.20 The INFORMATION_SCHEMA INNODB_INDEXES Table"> <code class="literal"> INNODB_INDEXES </code> </a> table. For example: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa50025705"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_INDEXES <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span><span class="token operator">=</span><span class="token string">'id_index'</span> \G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> INDEX_ID<span class="token punctuation">:</span> 91 NAME<span class="token punctuation">:</span> id_index TABLE_ID<span class="token punctuation">:</span> 68 TYPE<span class="token punctuation">:</span> 0 N_FIELDS<span class="token punctuation">:</span> 1 PAGE_NO<span class="token punctuation">:</span> 4 SPACE<span class="token punctuation">:</span> 57 MERGE_THRESHOLD<span class="token punctuation">:</span> 40</span></code></pre> </div> <p> You can use <a class="link" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement"> <code class="literal"> SHOW CREATE TABLE </code> </a> to view the <code class="literal"> MERGE_THRESHOLD </code> value for a table, if explicitly defined using the <em class="replaceable"> <code> table_option </code> </em> <code class="literal"> COMMENT </code> clause: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa97733350"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t2 \G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Table<span class="token punctuation">:</span> t2 Create Table<span class="token punctuation">:</span> CREATE TABLE `t2` ( `id` int(11) DEFAULT NULL, KEY `id_index` (`id`) COMMENT 'MERGE_THRESHOLD=40' ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci</span></code></pre> </div> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> A <code class="literal"> MERGE_THRESHOLD </code> value defined at the index level takes priority over a <code class="literal"> MERGE_THRESHOLD </code> value defined for the table. If undefined, <code class="literal"> MERGE_THRESHOLD </code> defaults to 50% ( <code class="literal"> MERGE_THRESHOLD=50 </code> , which is the previously hardcoded value. </p> </div> <p> Likewise, you can use <a class="link" href="show-index.html" title="15.7.7.23 SHOW INDEX Statement"> <code class="literal"> SHOW INDEX </code> </a> to view the <code class="literal"> MERGE_THRESHOLD </code> value for an index, if explicitly defined using the <em class="replaceable"> <code> index_option </code> </em> <code class="literal"> COMMENT </code> clause: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa86304780"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">INDEX</span> <span class="token keyword">FROM</span> t2 \G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation">*</span> Table<span class="token punctuation">:</span> t2 Non_unique<span class="token punctuation">:</span> 1 Key_name<span class="token punctuation">:</span> id_index Seq_in_index<span class="token punctuation">:</span> 1 Column_name<span class="token punctuation">:</span> id Collation<span class="token punctuation">:</span> A Cardinality<span class="token punctuation">:</span> 0 Sub_part<span class="token punctuation">:</span> NULL Packed<span class="token punctuation">:</span> NULL Null<span class="token punctuation">:</span> YES Index_type<span class="token punctuation">:</span> BTREE Comment<span class="token punctuation">:</span> Index_comment<span class="token punctuation">:</span> MERGE_THRESHOLD=40</span></code></pre> </div> <h4> <a name="idm46045161866784"> </a> Measuring the Effect of MERGE_THRESHOLD Settings </h4> <p> The <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table provides two counters that can be used to measure the effect of a <code class="literal"> MERGE_THRESHOLD </code> setting on index page merges. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44911639"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token keyword">NAME</span><span class="token punctuation">,</span> <span class="token keyword">COMMENT</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">like</span> <span class="token string">'%index_page_merge%'</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> NAME <span class="token punctuation">\|</span> COMMENT <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> index_page_merge_attempts <span class="token punctuation">\|</span> Number of index page merge attempts <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> index_page_merge_successful <span class="token punctuation">\|</span> Number of successful index page merges <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> <p> When lowering the <code class="literal"> MERGE_THRESHOLD </code> value, the objectives are: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> A smaller number of page merge attempts and successful page merges </p> </li> <li class="listitem"> <p> A similar number of page merge attempts and successful page merges </p> </li> </ul> </div> <p> A <code class="literal"> MERGE_THRESHOLD </code> setting that is too small could result in large data files due to an excessive amount of empty page space. </p> <p> For information about using <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> counters, see <a class="xref" href="innodb-information-schema-metrics-table.html" title="17.15.6 InnoDB INFORMATION_SCHEMA Metrics Table"> Section 17.15.6, “InnoDB INFORMATION_SCHEMA Metrics Table” </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/federated-description.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="federated-description"> </a> 18.8.1 FEDERATED Storage Engine Overview </h3> </div> </div> </div> <p> When you create a table using one of the standard storage engines (such as <code class="literal"> MyISAM </code> , <code class="literal"> CSV </code> or <code class="literal"> InnoDB </code> ), the table consists of the table definition and the associated data. When you create a <code class="literal"> FEDERATED </code> table, the table definition is the same, but the physical storage of the data is handled on a remote server. </p> <p> A <code class="literal"> FEDERATED </code> table consists of two elements: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> A <span class="emphasis"> <em> remote server </em> </span> with a database table, which in turn consists of the table definition (stored in the MySQL data dictionary) and the associated table. The table type of the remote table may be any type supported by the remote <code class="literal"> mysqld </code> server, including <code class="literal"> MyISAM </code> or <code class="literal"> InnoDB </code> . </p> </li> <li class="listitem"> <p> A <span class="emphasis"> <em> local server </em> </span> with a database table, where the table definition matches that of the corresponding table on the remote server. The table definition is stored in the data dictionary. There is no data file on the local server. Instead, the table definition includes a connection string that points to the remote table. </p> </li> </ul> </div> <p> When executing queries and statements on a <code class="literal"> FEDERATED </code> table on the local server, the operations that would normally insert, update or delete information from a local data file are instead sent to the remote server for execution, where they update the data file on the remote server or return matching rows from the remote server. </p> <p> The basic structure of a <code class="literal"> FEDERATED </code> table setup is shown in <a class="xref" href="federated-description.html#figure-se-federated-structure" title="Figure 18.2 FEDERATED Table Structure"> Figure 18.2, “FEDERATED Table Structure” </a> . </p> <div class="figure"> <a name="figure-se-federated-structure"> </a> <p class="title"> <b> Figure 18.2 FEDERATED Table Structure </b> </p> <div class="figure-contents"> <div class="mediaobject"> <img alt="Content is described in the surrounding text." src="images/se-federated-structure.png" style="width: 100%; max-width: 384px;"/> </div> </div> </div> <br class="figure-break"/> <p> When a client issues an SQL statement that refers to a <code class="literal"> FEDERATED </code> table, the flow of information between the local server (where the SQL statement is executed) and the remote server (where the data is physically stored) is as follows: </p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p> The storage engine looks through each column that the <code class="literal"> FEDERATED </code> table has and constructs an appropriate SQL statement that refers to the remote table. </p> </li> <li class="listitem"> <p> The statement is sent to the remote server using the MySQL client API. </p> </li> <li class="listitem"> <p> The remote server processes the statement and the local server retrieves any result that the statement produces (an affected-rows count or a result set). </p> </li> <li class="listitem"> <p> If the statement produces a result set, each column is converted to internal storage engine format that the <code class="literal"> FEDERATED </code> engine expects and can use to display the result to the client that issued the original statement. </p> </li> </ol> </div> <p> The local server communicates with the remote server using MySQL client C API functions. It invokes <a class="ulink" href="/doc/c-api/8.4/en/mysql-real-query.html" target="_top"> <code class="literal"> mysql_real_query() </code> </a> to send the statement. To read a result set, it uses <a class="ulink" href="/doc/c-api/8.4/en/mysql-store-result.html" target="_top"> <code class="literal"> mysql_store_result() </code> </a> and fetches rows one at a time using <a class="ulink" href="/doc/c-api/8.4/en/mysql-fetch-row.html" target="_top"> <code class="literal"> mysql_fetch_row() </code> </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-dict-obj-info.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysql-cluster-ndbinfo-dict-obj-info"> </a> 25.6.17.25 The ndbinfo dict_obj_info Table </h4> </div> </div> </div> <a class="indexterm" name="idm46045089672720"> </a> <p> The <code class="literal"> dict_obj_info </code> table provides information about <code class="literal"> NDB </code> data dictionary ( <a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbdict.html" target="_top"> <code class="literal"> DICT </code> </a> ) objects such as tables and indexes. (The <a class="link" href="mysql-cluster-ndbinfo-dict-obj-types.html" title="25.6.17.27 The ndbinfo dict_obj_types Table"> <code class="literal"> dict_obj_types </code> </a> table can be queried for a list of all the types.) This information includes the object's type, state, parent object (if any), and fully qualified name. </p> <p> The <code class="literal"> dict_obj_info </code> table contains the following columns: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> type </code> </p> <p> Type of <a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbdict.html" target="_top"> <code class="literal"> DICT </code> </a> object; join on <a class="link" href="mysql-cluster-ndbinfo-dict-obj-types.html" title="25.6.17.27 The ndbinfo dict_obj_types Table"> <code class="literal"> dict_obj_types </code> </a> to obtain the name </p> </li> <li class="listitem"> <p> <code class="literal"> id </code> </p> <p> Object identifier; for Disk Data undo log files and data files, this is the same as the value shown in the <code class="literal"> LOGFILE_GROUP_NUMBER </code> column of the Information Schema <a class="link" href="information-schema-files-table.html" title="28.3.15 The INFORMATION_SCHEMA FILES Table"> <code class="literal"> FILES </code> </a> table; for undo log files, it also the same as the value shown for the <code class="literal"> log_id </code> column in the <code class="literal"> ndbinfo </code> <a class="link" href="mysql-cluster-ndbinfo-logbuffers.html" title="25.6.17.43 The ndbinfo logbuffers Table"> <code class="literal"> logbuffers </code> </a> and <a class="link" href="mysql-cluster-ndbinfo-logspaces.html" title="25.6.17.44 The ndbinfo logspaces Table"> <code class="literal"> logspaces </code> </a> tables </p> </li> <li class="listitem"> <p> <code class="literal"> version </code> </p> <p> Object version </p> </li> <li class="listitem"> <p> <code class="literal"> state </code> </p> <p> Object state; see <a class="ulink" href="/doc/ndbapi/en/ndb-object.html#ndb-object-state" target="_top"> Object::State </a> for values and descriptions. </p> </li> <li class="listitem"> <p> <code class="literal"> parent_obj_type </code> </p> <p> Parent object's type (a <code class="literal"> dict_obj_types </code> type ID); 0 indicates that the object has no parent </p> </li> <li class="listitem"> <p> <code class="literal"> parent_obj_id </code> </p> <p> Parent object ID (such as a base table); 0 indicates that the object has no parent </p> </li> <li class="listitem"> <p> <code class="literal"> fq_name </code> </p> <p> Fully qualified object name; for a table, this has the form <code class="literal"> <em class="replaceable"> <code> database_name </code> </em> /def/ <em class="replaceable"> <code> table_name </code> </em> </code> , for a primary key, the form is <code class="literal"> sys/def/ <em class="replaceable"> <code> table_id </code> </em> /PRIMARY </code> , and for a unique key it is <code class="literal"> sys/def/ <em class="replaceable"> <code> table_id </code> </em> / <em class="replaceable"> <code> uk_name </code> </em> $unique </code> </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-ft-config-table.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="information-schema-innodb-ft-config-table"> </a> 28.4.15 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table </h3> </div> </div> </div> <a class="indexterm" name="idm46045076930576"> </a> <p> The <a class="link" href="information-schema-innodb-ft-config-table.html" title="28.4.15 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table"> <code class="literal"> INNODB_FT_CONFIG </code> </a> table provides metadata about the <code class="literal"> FULLTEXT </code> index and associated processing for an <code class="literal"> InnoDB </code> table. </p> <p> This table is empty initially. Before querying it, set the value of the <a class="link" href="innodb-parameters.html#sysvar_innodb_ft_aux_table"> <code class="literal"> innodb_ft_aux_table </code> </a> system variable to the name (including the database name) of the table that contains the <code class="literal"> FULLTEXT </code> index (for example, <code class="literal"> test/articles </code> ). </p> <p> For related usage information and examples, see <a class="xref" href="innodb-information-schema-fulltext_index-tables.html" title="17.15.4 InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables"> Section 17.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables” </a> . </p> <p> The <a class="link" href="information-schema-innodb-ft-config-table.html" title="28.4.15 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table"> <code class="literal"> INNODB_FT_CONFIG </code> </a> table has these columns: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> KEY </code> </p> <p> The name designating an item of metadata for an <code class="literal"> InnoDB </code> table containing a <code class="literal"> FULLTEXT </code> index. </p> <p> The values for this column might change, depending on the needs for performance tuning and debugging for <code class="literal"> InnoDB </code> full-text processing. The key names and their meanings include: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> <code class="literal"> optimize_checkpoint_limit </code> : The number of seconds after which an <a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement"> <code class="literal"> OPTIMIZE TABLE </code> </a> run stops. </p> </li> <li class="listitem"> <p> <code class="literal"> synced_doc_id </code> : The next <code class="literal"> DOC_ID </code> to be issued. </p> </li> <li class="listitem"> <p> <code class="literal"> stopword_table_name </code> : The <em class="replaceable"> <code> database/table </code> </em> name for a user-defined stopword table. The <code class="literal"> VALUE </code> column is empty if there is no user-defined stopword table. </p> </li> <li class="listitem"> <p> <code class="literal"> use_stopword </code> : Indicates whether a stopword table is used, which is defined when the <code class="literal"> FULLTEXT </code> index is created. </p> </li> </ul> </div> </li> <li class="listitem"> <p> <code class="literal"> VALUE </code> </p> <p> The value associated with the corresponding <code class="literal"> KEY </code> column, reflecting some limit or current value for an aspect of a <code class="literal"> FULLTEXT </code> index for an <code class="literal"> InnoDB </code> table. </p> </li> </ul> </div> <h4> <a name="idm46045076899952"> </a> Example </h4> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa71628088"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_FT_CONFIG<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> KEY <span class="token punctuation">\|</span> VALUE <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> optimize_checkpoint_limit <span class="token punctuation">\|</span> 180 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> synced_doc_id <span class="token punctuation">\|</span> 0 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> stopword_table_name <span class="token punctuation">\|</span> test/my_stopwords <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> use_stopword <span class="token punctuation">\|</span> 1 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> <h4> <a name="idm46045076897200"> </a> Notes </h4> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> This table is intended only for internal configuration. It is not intended for statistical information purposes. </p> </li> <li class="listitem"> <p> You must have the <a class="link" href="privileges-provided.html#priv_process"> <code class="literal"> PROCESS </code> </a> privilege to query this table. </p> </li> <li class="listitem"> <p> Use the <code class="literal"> INFORMATION_SCHEMA </code> <a class="link" href="information-schema-columns-table.html" title="28.3.8 The INFORMATION_SCHEMA COLUMNS Table"> <code class="literal"> COLUMNS </code> </a> table or the <a class="link" href="show-columns.html" title="15.7.7.6 SHOW COLUMNS Statement"> <code class="literal"> SHOW COLUMNS </code> </a> statement to view additional information about the columns of this table, including data types and default values. </p> </li> <li class="listitem"> <p> For more information about <code class="literal"> InnoDB </code> <code class="literal"> FULLTEXT </code> search, see <a class="xref" href="innodb-fulltext-index.html" title="17.6.2.4 InnoDB Full-Text Indexes"> Section 17.6.2.4, “InnoDB Full-Text Indexes” </a> , and <a class="xref" href="fulltext-search.html" title="14.9 Full-Text Search Functions"> Section 14.9, “Full-Text Search Functions” </a> . </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/thread-pool-elements.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="thread-pool-elements"> </a> 7.6.3.1 Thread Pool Elements </h4> </div> </div> </div> <a class="indexterm" name="idm46045256857264"> </a> <p> MySQL Enterprise Thread Pool comprises these elements: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> A plugin library file implements a plugin for the thread pool code as well as several associated monitoring tables that provide information about thread pool operation: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> In MySQL 8.4, the monitoring tables are Performance Schema tables; see <a class="xref" href="performance-schema-thread-pool-tables.html" title="29.12.16 Performance Schema Thread Pool Tables"> Section 29.12.16, “Performance Schema Thread Pool Tables” </a> . </p> </li> <li class="listitem"> <p> In older versions of MySQL, the monitoring tables were <code class="literal"> INFORMATION_SCHEMA </code> tables (see <a class="xref" href="thread-pool-information-schema-tables.html" title="28.5 INFORMATION_SCHEMA Thread Pool Tables"> Section 28.5, “INFORMATION_SCHEMA Thread Pool Tables” </a> ). The <code class="literal"> INFORMATION_SCHEMA </code> tables are deprecated; expect them to be removed in a future version of MySQL. Applications should transition away from the <code class="literal"> INFORMATION_SCHEMA </code> tables to the Performance Schema tables. For example, if an application uses this query: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa36939135"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>TP_THREAD_STATE<span class="token punctuation">;</span></code></pre> </div> <p> The application should use this query instead: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa66787753"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>tp_thread_state<span class="token punctuation">;</span></code></pre> </div> </li> </ul> </div> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> If you do not load all the monitoring tables, some or all MySQL Enterprise Monitor thread pool graphs may be empty. </p> </div> <p> For a detailed description of how the thread pool works, see <a class="xref" href="thread-pool-operation.html" title="7.6.3.3 Thread Pool Operation"> Section 7.6.3.3, “Thread Pool Operation” </a> . </p> </li> <li class="listitem"> <p> Several system variables are related to the thread pool. The <a class="link" href="server-system-variables.html#sysvar_thread_handling"> <code class="literal"> thread_handling </code> </a> system variable has a value of <code class="literal"> loaded-dynamically </code> when the server successfully loads the thread pool plugin. </p> <p> The other related system variables are implemented by the thread pool plugin and are not available unless it is enabled. For information about using these variables, see <a class="xref" href="thread-pool-operation.html" title="7.6.3.3 Thread Pool Operation"> Section 7.6.3.3, “Thread Pool Operation” </a> , and <a class="xref" href="thread-pool-tuning.html" title="7.6.3.4 Thread Pool Tuning"> Section 7.6.3.4, “Thread Pool Tuning” </a> . </p> </li> <li class="listitem"> <p> The Performance Schema has instruments that expose information about the thread pool and may be used to investigate operational performance. To identify them, use this query: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63151090"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>setup_instruments <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">'%thread_pool%'</span><span class="token punctuation">;</span></code></pre> </div> <p> For more information, see <a class="xref" href="performance-schema.html" title="Chapter 29 MySQL Performance Schema"> Chapter 29, <i> MySQL Performance Schema </i> </a> . </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/mysqlbinlog-hexdump.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysqlbinlog-hexdump"> </a> 6.6.9.1 mysqlbinlog Hex Dump Format </h4> </div> </div> </div> <p> The <a class="link" href="mysqlbinlog.html#option_mysqlbinlog_hexdump"> <code class="option"> --hexdump </code> </a> option causes <a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files"> <span class="command"> <strong> mysqlbinlog </strong> </span> </a> to produce a hex dump of the binary log contents: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa17215586"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqlbinlog <span class="token property">--hexdump</span> source-bin<span class="token punctuation">.</span>000001</code></pre> </div> <p> The hex output consists of comment lines beginning with <code class="literal"> # </code> , so the output might look like this for the preceding command: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa96387263"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token comment" spellcheck="true">/!40019 SET @@SESSION.max_insert_delayed_threads=0/</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true">/!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0/</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true"># at 4</span> <span class="token comment" spellcheck="true">#051024 17:24:13 server id 1 end_log_pos 98</span> <span class="token comment" spellcheck="true"># Position Timestamp Type Master ID Size Master Pos Flags</span> <span class="token comment" spellcheck="true"># 00000004 9d fc 5c 43 0f 01 00 00 00 5e 00 00 00 62 00 00 00 00 00</span> <span class="token comment" spellcheck="true"># 00000017 04 00 35 2e 30 2e 31 35 2d 64 65 62 75 67 2d 6c \|..5.0.15.debug.l\|</span> <span class="token comment" spellcheck="true"># 00000027 6f 67 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \|og..............\|</span> <span class="token comment" spellcheck="true"># 00000037 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \|................\|</span> <span class="token comment" spellcheck="true"># 00000047 00 00 00 00 9d fc 5c 43 13 38 0d 00 08 00 12 00 \|.......C.8......\|</span> <span class="token comment" spellcheck="true"># 00000057 04 04 04 04 12 00 00 4b 00 04 1a \|.......K...\|</span> <span class="token comment" spellcheck="true"># Start: binlog v 4, server v 5.0.15-debug-log created 051024 17:24:13</span> <span class="token comment" spellcheck="true"># at startup</span> <span class="token keyword">ROLLBACK</span><span class="token punctuation">;</span></code></pre> </div> <p> Hex dump output currently contains the elements in the following list. This format is subject to change. For more information about binary log format, see <a class="ulink" href="/doc/internals/en/binary-log.html" target="_top"> MySQL Internals: The Binary Log </a> . </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> Position </code> : The byte position within the log file. </p> </li> <li class="listitem"> <p> <code class="literal"> Timestamp </code> : The event timestamp. In the example shown, <code class="literal"> '9d fc 5c 43' </code> is the representation of <code class="literal"> '051024 17:24:13' </code> in hexadecimal. </p> </li> <li class="listitem"> <p> <code class="literal"> Type </code> : The event type code. </p> </li> <li class="listitem"> <p> <code class="literal"> Master ID </code> : The server ID of the replication source server that created the event. </p> </li> <li class="listitem"> <p> <code class="literal"> Size </code> : The size in bytes of the event. </p> </li> <li class="listitem"> <p> <code class="literal"> Master Pos </code> : The position of the next event in the original source's binary log file. </p> </li> <li class="listitem"> <p> <code class="literal"> Flags </code> : Event flag values. </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/innodb-deadlock-detection.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="innodb-deadlock-detection"> </a> 17.7.5.2 Deadlock Detection </h4> </div> </div> </div> <a class="indexterm" name="idm46045163763152"> </a> <a class="indexterm" name="idm46045163761664"> </a> <a class="indexterm" name="idm46045163760592"> </a> <a class="indexterm" name="idm46045163759104"> </a> <a class="indexterm" name="idm46045163757200"> </a> <a class="indexterm" name="idm46045163755712"> </a> <p> When <a class="link" href="glossary.html#glos_deadlock_detection" title="deadlock detection"> deadlock detection </a> is enabled (the default), <code class="literal"> InnoDB </code> automatically detects transaction <a class="link" href="glossary.html#glos_deadlock" title="deadlock"> deadlocks </a> and rolls back a transaction or transactions to break the deadlock. <code class="literal"> InnoDB </code> tries to pick small transactions to roll back, where the size of a transaction is determined by the number of rows inserted, updated, or deleted. </p> <p> <code class="literal"> InnoDB </code> is aware of table locks if <code class="literal"> innodb_table_locks = 1 </code> (the default) and <a class="link" href="server-system-variables.html#sysvar_autocommit"> <code class="literal"> autocommit = 0 </code> </a> , and the MySQL layer above it knows about row-level locks. Otherwise, <code class="literal"> InnoDB </code> cannot detect deadlocks where a table lock set by a MySQL <a class="link" href="lock-tables.html" title="15.3.6 LOCK TABLES and UNLOCK TABLES Statements"> <code class="literal"> LOCK TABLES </code> </a> statement or a lock set by a storage engine other than <code class="literal"> InnoDB </code> is involved. Resolve these situations by setting the value of the <a class="link" href="innodb-parameters.html#sysvar_innodb_lock_wait_timeout"> <code class="literal"> innodb_lock_wait_timeout </code> </a> system variable. </p> <p> If the <code class="literal"> LATEST DETECTED DEADLOCK </code> section of <code class="literal"> InnoDB </code> Monitor output includes a message stating <span class="errortext"> TOO DEEP OR LONG SEARCH IN THE LOCK TABLE WAITS-FOR GRAPH, WE WILL ROLL BACK FOLLOWING TRANSACTION </span> , this indicates that the number of transactions on the wait-for list has reached a limit of 200. A wait-for list that exceeds 200 transactions is treated as a deadlock and the transaction attempting to check the wait-for list is rolled back. The same error may also occur if the locking thread must look at more than 1,000,000 locks owned by transactions on the wait-for list. </p> <p> For techniques to organize database operations to avoid deadlocks, see <a class="xref" href="innodb-deadlocks.html" title="17.7.5 Deadlocks in InnoDB"> Section 17.7.5, “Deadlocks in InnoDB” </a> . </p> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="innodb-disable-deadlock-detection"> </a> Disabling Deadlock Detection </h5> </div> </div> </div> <p> On high concurrency systems, deadlock detection can cause a slowdown when numerous threads wait for the same lock. At times, it may be more efficient to disable deadlock detection and rely on the <a class="link" href="innodb-parameters.html#sysvar_innodb_lock_wait_timeout"> <code class="literal"> innodb_lock_wait_timeout </code> </a> setting for transaction rollback when a deadlock occurs. Deadlock detection can be disabled using the <a class="link" href="innodb-parameters.html#sysvar_innodb_deadlock_detect"> <code class="literal"> innodb_deadlock_detect </code> </a> variable. </p> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/innodb-online-ddl.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="innodb-online-ddl"> </a> 17.12 InnoDB and Online DDL </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <span class="section"> <a href="innodb-online-ddl-operations.html"> 17.12.1 Online DDL Operations </a> </span> </dt> <dt> <span class="section"> <a href="innodb-online-ddl-performance.html"> 17.12.2 Online DDL Performance and Concurrency </a> </span> </dt> <dt> <span class="section"> <a href="innodb-online-ddl-space-requirements.html"> 17.12.3 Online DDL Space Requirements </a> </span> </dt> <dt> <span class="section"> <a href="online-ddl-memory-management.html"> 17.12.4 Online DDL Memory Management </a> </span> </dt> <dt> <span class="section"> <a href="online-ddl-parallel-thread-configuration.html"> 17.12.5 Configuring Parallel Threads for Online DDL Operations </a> </span> </dt> <dt> <span class="section"> <a href="innodb-online-ddl-single-multi.html"> 17.12.6 Simplifying DDL Statements with Online DDL </a> </span> </dt> <dt> <span class="section"> <a href="innodb-online-ddl-failure-conditions.html"> 17.12.7 Online DDL Failure Conditions </a> </span> </dt> <dt> <span class="section"> <a href="innodb-online-ddl-limitations.html"> 17.12.8 Online DDL Limitations </a> </span> </dt> </dl> </div> <a class="indexterm" name="idm46045160573136"> </a> <a class="indexterm" name="idm46045160572064"> </a> <p> The online DDL feature provides support for instant and in-place table alterations and concurrent DML. Benefits of this feature include: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> Improved responsiveness and availability in busy production environments, where making a table unavailable for minutes or hours is not practical. </p> </li> <li class="listitem"> <p> For in-place operations, the ability to adjust the balance between performance and concurrency during DDL operations using the <code class="literal"> LOCK </code> clause. See <a class="xref" href="innodb-online-ddl-performance.html#innodb-online-ddl-locking-options" title="The LOCK clause"> The LOCK clause </a> . </p> </li> <li class="listitem"> <p> Less disk space usage and I/O overhead than the table-copy method. </p> </li> </ul> </div> <p> Typically, you do not need to do anything special to enable online DDL. By default, MySQL performs the operation instantly or in place, as permitted, with as little locking as possible. </p> <p> You can control aspects of a DDL operation using the <code class="literal"> ALGORITHM </code> and <code class="literal"> LOCK </code> clauses of the <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> statement. These clauses are placed at the end of the statement, separated from the table and column specifications by commas. For example: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa61546769"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em> <span class="token keyword">ADD</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span><span class="token keyword"><em class="replaceable">column</em></span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">ALGORITHM</span><span class="token operator">=</span><span class="token keyword">INPLACE</span><span class="token punctuation">;</span></code></pre> </div> <p> The <code class="literal"> LOCK </code> clause may be used for operations that are performed in place and is useful for fine-tuning the degree of concurrent access to the table during operations. Only <code class="literal"> LOCK=DEFAULT </code> is supported for operations that are performed instantly. The <code class="literal"> ALGORITHM </code> clause is primarily intended for performance comparisons and as a fallback to the older table-copying behavior in case you encounter any issues. For example: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> To avoid accidentally making the table unavailable for reads, writes, or both, during an in-place <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> operation, specify a clause on the <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> statement such as <code class="literal"> LOCK=NONE </code> (permit reads and writes) or <code class="literal"> LOCK=SHARED </code> (permit reads). The operation halts immediately if the requested level of concurrency is not available. </p> </li> <li class="listitem"> <p> To compare performance between algorithms, run a statement with <code class="literal"> ALGORITHM=INSTANT </code> , <code class="literal"> ALGORITHM=INPLACE </code> and <code class="literal"> ALGORITHM=COPY </code> . You can also run a statement with the <a class="link" href="server-system-variables.html#sysvar_old_alter_table"> <code class="literal"> old_alter_table </code> </a> configuration option enabled to force the use of <code class="literal"> ALGORITHM=COPY </code> . </p> </li> <li class="listitem"> <p> To avoid tying up the server with an <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> operation that copies the table, include <code class="literal"> ALGORITHM=INSTANT </code> or <code class="literal"> ALGORITHM=INPLACE </code> . The statement halts immediately if it cannot use the specified algorithm. </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/clone-plugin-compressed-data.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="clone-plugin-compressed-data"> </a> 7.6.7.6 Cloning Compressed Data </h4> </div> </div> </div> <a class="indexterm" name="idm46045255409888"> </a> <p> Cloning of page-compressed data is supported. The following requirements apply when cloning remote data: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> The recipient file system must support sparse files and hole punching for hole punching to occur on the recipient. </p> </li> <li class="listitem"> <p> The donor and recipient file systems must have the same block size. If file system block sizes differ, an error similar to the following is reported: <span class="errortext"> ERROR 3868 (HY000): Clone Configuration FS Block Size: Donor value: 114688 is different from Recipient value: 4096 </span> . </p> </li> </ul> </div> <p> For information about the page compression feature, see <a class="xref" href="innodb-page-compression.html" title="17.9.2 InnoDB Page Compression"> Section 17.9.2, “InnoDB Page Compression” </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/apis-ruby-mysqlruby.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="apis-ruby-mysqlruby"> </a> 31.11.1 The MySQL/Ruby API </h3> </div> </div> </div> <p> The MySQL/Ruby module provides access to MySQL databases using Ruby through <code class="literal"> libmysqlclient </code> . </p> <p> For information on installing the module, and the functions exposed, see <a class="ulink" href="http://tmtm.org/en/mysql/ruby/" target="_blank"> MySQL/Ruby </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/faqs-virtualization.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="faqs-virtualization"> </a> A.18 MySQL 8.4 FAQ: Virtualization Support </h2> </div> </div> </div> <a class="indexterm" name="idm46045054794736"> </a> <div class="qandaset"> <a name="idm46045054793280"> </a> <dl> <dt> A.18.1. <a href="faqs-virtualization.html#faq-virtualization-support"> Is MySQL supported on virtualized environments such as Oracle VM, VMWare, Docker, Microsoft Hyper-V, or others? </a> </dt> </dl> <table border="0" style="width: 100%;"> <colgroup> <col align="left" width="1%"/> <col/> </colgroup> <tbody> <tr class="question"> <td align="left" valign="top"> <a name="faq-virtualization-support"> </a> <a name="idm46045054792464"> </a> <p> <b> A.18.1. </b> </p> </td> <td align="left" valign="top"> <p> Is MySQL supported on virtualized environments such as Oracle VM, VMWare, Docker, Microsoft Hyper-V, or others? </p> </td> </tr> <tr class="answer"> <td align="left" valign="top"> </td> <td align="left" valign="top"> <p> MySQL is supported on virtualized environments, but is certified only for <a class="ulink" href="http://www.oracle.com/technetwork/server-storage/vm/index.html" target="_blank"> Oracle VM </a> . Contact Oracle Support for more information. </p> <p> Be aware of potential problems when using virtualization software. The usual ones are related to performance, performance degradations, slowness, or unpredictability of disk, I/O, network, and memory. </p> </td> </tr> </tbody> </table> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/reset.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="reset"> </a> 15.7.8.6 RESET Statement </h4> </div> </div> </div> <a class="indexterm" name="idm46045168375264"> </a> <a class="indexterm" name="idm46045168374176"> </a> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa39287278"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">RESET</span> <em class="replaceable">reset_option</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">reset_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <em class="replaceable">reset_option</em>: { <span class="token datatype">BINARY</span> <span class="token keyword">LOGS</span> <span class="token operator">AND</span> GTIDS <span class="token operator">\|</span> <span class="token keyword">REPLICA</span> }</code></pre> </div> <p> The <a class="link" href="reset.html" title="15.7.8.6 RESET Statement"> <code class="literal"> RESET </code> </a> statement is used to clear the state of various server operations. You must have the <a class="link" href="privileges-provided.html#priv_reload"> <code class="literal"> RELOAD </code> </a> privilege to execute <a class="link" href="reset.html" title="15.7.8.6 RESET Statement"> <code class="literal"> RESET </code> </a> . </p> <p> For information about the <a class="link" href="reset-persist.html" title="15.7.8.7 RESET PERSIST Statement"> <code class="literal"> RESET PERSIST </code> </a> statement that removes persisted global system variables, see <a class="xref" href="reset-persist.html" title="15.7.8.7 RESET PERSIST Statement"> Section 15.7.8.7, “RESET PERSIST Statement” </a> . </p> <p> <a class="link" href="reset.html" title="15.7.8.6 RESET Statement"> <code class="literal"> RESET </code> </a> acts as a stronger version of the <a class="link" href="flush.html" title="15.7.8.3 FLUSH Statement"> <code class="literal"> FLUSH </code> </a> statement. See <a class="xref" href="flush.html" title="15.7.8.3 FLUSH Statement"> Section 15.7.8.3, “FLUSH Statement” </a> . </p> <p> The <a class="link" href="reset.html" title="15.7.8.6 RESET Statement"> <code class="literal"> RESET </code> </a> statement causes an implicit commit. See <a class="xref" href="implicit-commit.html" title="15.3.3 Statements That Cause an Implicit Commit"> Section 15.3.3, “Statements That Cause an Implicit Commit” </a> . </p> <p> The following list describes the permitted <a class="link" href="reset.html" title="15.7.8.6 RESET Statement"> <code class="literal"> RESET </code> </a> statement <em class="replaceable"> <code> reset_option </code> </em> values: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <a class="link" href="reset-binary-logs-and-gtids.html" title="15.4.1.2 RESET BINARY LOGS AND GTIDS Statement"> <code class="literal"> RESET BINARY LOGS AND GTIDS </code> </a> </p> <p> Deletes all binary logs listed in the index file, resets the binary log index file to be empty, and creates a new binary log file. </p> </li> <li class="listitem"> <p> <a class="link" href="reset-replica.html" title="15.4.2.3 RESET REPLICA Statement"> <code class="literal"> RESET REPLICA </code> </a> </p> <p> Makes the replica forget its replication position in the source binary logs. Also resets the relay log by deleting any existing relay log files and beginning a new one. </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/firewall-information-schema-tables.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="firewall-information-schema-tables"> </a> 28.7 INFORMATION_SCHEMA MySQL Enterprise Firewall Tables </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <span class="section"> <a href="information-schema-firewall-table-reference.html"> 28.7.1 INFORMATION_SCHEMA Firewall Table Reference </a> </span> </dt> <dt> <span class="section"> <a href="information-schema-mysql-firewall-users-table.html"> 28.7.2 The INFORMATION_SCHEMA MYSQL_FIREWALL_USERS Table </a> </span> </dt> <dt> <span class="section"> <a href="information-schema-mysql-firewall-whitelist-table.html"> 28.7.3 The INFORMATION_SCHEMA MYSQL_FIREWALL_WHITELIST Table </a> </span> </dt> </dl> </div> <a class="indexterm" name="idm46045075980752"> </a> <p> The following sections describe the <code class="literal"> INFORMATION_SCHEMA </code> tables associated with MySQL Enterprise Firewall (see <a class="xref" href="firewall.html" title="8.4.7 MySQL Enterprise Firewall"> Section 8.4.7, “MySQL Enterprise Firewall” </a> ). They provide views into the firewall in-memory data cache. These tables are available only if the appropriate firewall plugins are enabled. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/linux-installation-juju.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="linux-installation-juju"> </a> 2.5.8 Installing MySQL on Linux with Juju </h3> </div> </div> </div> <p> The Juju deployment framework supports easy installation and configuration of MySQL servers. For instructions, see <a class="ulink" href="https://jujucharms.com/mysql/" target="_blank"> https://jujucharms.com/mysql/ </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-buffer-pool-stats-table.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="information-schema-innodb-buffer-pool-stats-table"> </a> 28.4.4 The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table </h3> </div> </div> </div> <a class="indexterm" name="idm46045077425312"> </a> <p> The <a class="link" href="information-schema-innodb-buffer-pool-stats-table.html" title="28.4.4 The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table"> <code class="literal"> INNODB_BUFFER_POOL_STATS </code> </a> table provides much of the same buffer pool information provided in <a class="link" href="show-engine.html" title="15.7.7.16 SHOW ENGINE Statement"> <code class="literal"> SHOW ENGINE INNODB STATUS </code> </a> output. Much of the same information may also be obtained using <code class="literal"> InnoDB </code> buffer pool <a class="link" href="server-status-variables.html" title="7.1.10 Server Status Variables"> server status variables </a> . </p> <p> The idea of making pages in the buffer pool <span class="quote"> “ <span class="quote"> young </span> ” </span> or <span class="quote"> “ <span class="quote"> not young </span> ” </span> refers to transferring them between the <a class="link" href="glossary.html#glos_sublist" title="sublist"> sublists </a> at the head and tail of the buffer pool data structure. Pages made <span class="quote"> “ <span class="quote"> young </span> ” </span> take longer to age out of the buffer pool, while pages made <span class="quote"> “ <span class="quote"> not young </span> ” </span> are moved much closer to the point of <a class="link" href="glossary.html#glos_eviction" title="eviction"> eviction </a> . </p> <p> For related usage information and examples, see <a class="xref" href="innodb-information-schema-buffer-pool-tables.html" title="17.15.5 InnoDB INFORMATION_SCHEMA Buffer Pool Tables"> Section 17.15.5, “InnoDB INFORMATION_SCHEMA Buffer Pool Tables” </a> . </p> <p> The <a class="link" href="information-schema-innodb-buffer-pool-stats-table.html" title="28.4.4 The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table"> <code class="literal"> INNODB_BUFFER_POOL_STATS </code> </a> table has these columns: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> POOL_ID </code> </p> <p> The buffer pool ID. This is an identifier to distinguish between multiple buffer pool instances. </p> </li> <li class="listitem"> <p> <code class="literal"> POOL_SIZE </code> </p> <p> The <code class="literal"> InnoDB </code> buffer pool size in pages. </p> </li> <li class="listitem"> <p> <code class="literal"> FREE_BUFFERS </code> </p> <p> The number of free pages in the <code class="literal"> InnoDB </code> buffer pool. </p> </li> <li class="listitem"> <p> <code class="literal"> DATABASE_PAGES </code> </p> <p> The number of pages in the <code class="literal"> InnoDB </code> buffer pool containing data. This number includes both dirty and clean pages. </p> </li> <li class="listitem"> <p> <code class="literal"> OLD_DATABASE_PAGES </code> </p> <p> The number of pages in the <code class="literal"> old </code> buffer pool sublist. </p> </li> <li class="listitem"> <p> <code class="literal"> MODIFIED_DATABASE_PAGES </code> </p> <p> The number of modified (dirty) database pages. </p> </li> <li class="listitem"> <p> <code class="literal"> PENDING_DECOMPRESS </code> </p> <p> The number of pages pending decompression. </p> </li> <li class="listitem"> <p> <code class="literal"> PENDING_READS </code> </p> <p> The number of pending reads. </p> </li> <li class="listitem"> <p> <code class="literal"> PENDING_FLUSH_LRU </code> </p> <p> The number of pages pending flush in the LRU. </p> </li> <li class="listitem"> <p> <code class="literal"> PENDING_FLUSH_LIST </code> </p> <p> The number of pages pending flush in the flush list. </p> </li> <li class="listitem"> <p> <code class="literal"> PAGES_MADE_YOUNG </code> </p> <p> The number of pages made young. </p> </li> <li class="listitem"> <p> <code class="literal"> PAGES_NOT_MADE_YOUNG </code> </p> <p> The number of pages not made young. </p> </li> <li class="listitem"> <p> <code class="literal"> PAGES_MADE_YOUNG_RATE </code> </p> <p> The number of pages made young per second (pages made young since the last printout / time elapsed). </p> </li> <li class="listitem"> <p> <code class="literal"> PAGES_MADE_NOT_YOUNG_RATE </code> </p> <p> The number of pages not made per second (pages not made young since the last printout / time elapsed). </p> </li> <li class="listitem"> <p> <code class="literal"> NUMBER_PAGES_READ </code> </p> <p> The number of pages read. </p> </li> <li class="listitem"> <p> <code class="literal"> NUMBER_PAGES_CREATED </code> </p> <p> The number of pages created. </p> </li> <li class="listitem"> <p> <code class="literal"> NUMBER_PAGES_WRITTEN </code> </p> <p> The number of pages written. </p> </li> <li class="listitem"> <p> <code class="literal"> PAGES_READ_RATE </code> </p> <p> The number of pages read per second (pages read since the last printout / time elapsed). </p> </li> <li class="listitem"> <p> <code class="literal"> PAGES_CREATE_RATE </code> </p> <p> The number of pages created per second (pages created since the last printout / time elapsed). </p> </li> <li class="listitem"> <p> <code class="literal"> PAGES_WRITTEN_RATE </code> </p> <p> The number of pages written per second (pages written since the last printout / time elapsed). </p> </li> <li class="listitem"> <p> <code class="literal"> NUMBER_PAGES_GET </code> </p> <p> The number of logical read requests. </p> </li> <li class="listitem"> <p> <code class="literal"> HIT_RATE </code> </p> <p> The buffer pool hit rate. </p> </li> <li class="listitem"> <p> <code class="literal"> YOUNG_MAKE_PER_THOUSAND_GETS </code> </p> <p> The number of pages made young per thousand gets. </p> </li> <li class="listitem"> <p> <code class="literal"> NOT_YOUNG_MAKE_PER_THOUSAND_GETS </code> </p> <p> The number of pages not made young per thousand gets. </p> </li> <li class="listitem"> <p> <code class="literal"> NUMBER_PAGES_READ_AHEAD </code> </p> <p> The number of pages read ahead. </p> </li> <li class="listitem"> <p> <code class="literal"> NUMBER_READ_AHEAD_EVICTED </code> </p> <p> The number of pages read into the <code class="literal"> InnoDB </code> buffer pool by the read-ahead background thread that were subsequently evicted without having been accessed by queries. </p> </li> <li class="listitem"> <p> <code class="literal"> READ_AHEAD_RATE </code> </p> <p> The read-ahead rate per second (pages read ahead since the last printout / time elapsed). </p> </li> <li class="listitem"> <p> <code class="literal"> READ_AHEAD_EVICTED_RATE </code> </p> <p> The number of read-ahead pages evicted without access per second (read-ahead pages not accessed since the last printout / time elapsed). </p> </li> <li class="listitem"> <p> <code class="literal"> LRU_IO_TOTAL </code> </p> <p> Total LRU I/O. </p> </li> <li class="listitem"> <p> <code class="literal"> LRU_IO_CURRENT </code> </p> <p> LRU I/O for the current interval. </p> </li> <li class="listitem"> <p> <code class="literal"> UNCOMPRESS_TOTAL </code> </p> <p> The total number of pages decompressed. </p> </li> <li class="listitem"> <p> <code class="literal"> UNCOMPRESS_CURRENT </code> </p> <p> The number of pages decompressed in the current interval. </p> </li> </ul> </div> <h4> <a name="idm46045077346112"> </a> Example </h4> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75073322"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_BUFFER_POOL_STATS\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation">*</span> POOL_ID<span class="token punctuation">:</span> 0 POOL_SIZE<span class="token punctuation">:</span> 8192 FREE_BUFFERS<span class="token punctuation">:</span> 1 DATABASE_PAGES<span class="token punctuation">:</span> 8085 OLD_DATABASE_PAGES<span class="token punctuation">:</span> 2964 MODIFIED_DATABASE_PAGES<span class="token punctuation">:</span> 0 PENDING_DECOMPRESS<span class="token punctuation">:</span> 0 PENDING_READS<span class="token punctuation">:</span> 0 PENDING_FLUSH_LRU<span class="token punctuation">:</span> 0 PENDING_FLUSH_LIST<span class="token punctuation">:</span> 0 PAGES_MADE_YOUNG<span class="token punctuation">:</span> 22821 PAGES_NOT_MADE_YOUNG<span class="token punctuation">:</span> 3544303 PAGES_MADE_YOUNG_RATE<span class="token punctuation">:</span> 357.62602199870594 PAGES_MADE_NOT_YOUNG_RATE<span class="token punctuation">:</span> 0 NUMBER_PAGES_READ<span class="token punctuation">:</span> 2389 NUMBER_PAGES_CREATED<span class="token punctuation">:</span> 12385 NUMBER_PAGES_WRITTEN<span class="token punctuation">:</span> 13111 PAGES_READ_RATE<span class="token punctuation">:</span> 0 PAGES_CREATE_RATE<span class="token punctuation">:</span> 0 PAGES_WRITTEN_RATE<span class="token punctuation">:</span> 0 NUMBER_PAGES_GET<span class="token punctuation">:</span> 33322210 HIT_RATE<span class="token punctuation">:</span> 1000 YOUNG_MAKE_PER_THOUSAND_GETS<span class="token punctuation">:</span> 18 NOT_YOUNG_MAKE_PER_THOUSAND_GETS<span class="token punctuation">:</span> 0 NUMBER_PAGES_READ_AHEAD<span class="token punctuation">:</span> 2024 NUMBER_READ_AHEAD_EVICTED<span class="token punctuation">:</span> 0 READ_AHEAD_RATE<span class="token punctuation">:</span> 0 READ_AHEAD_EVICTED_RATE<span class="token punctuation">:</span> 0 LRU_IO_TOTAL<span class="token punctuation">:</span> 0 LRU_IO_CURRENT<span class="token punctuation">:</span> 0 UNCOMPRESS_TOTAL<span class="token punctuation">:</span> 0 UNCOMPRESS_CURRENT<span class="token punctuation">:</span> 0</span></code></pre> </div> <h4> <a name="idm46045077341184"> </a> Notes </h4> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> This table is useful primarily for expert-level performance monitoring, or when developing performance-related extensions for MySQL. </p> </li> <li class="listitem"> <p> You must have the <a class="link" href="privileges-provided.html#priv_process"> <code class="literal"> PROCESS </code> </a> privilege to query this table. </p> </li> <li class="listitem"> <p> Use the <code class="literal"> INFORMATION_SCHEMA </code> <a class="link" href="information-schema-columns-table.html" title="28.3.8 The INFORMATION_SCHEMA COLUMNS Table"> <code class="literal"> COLUMNS </code> </a> table or the <a class="link" href="show-columns.html" title="15.7.7.6 SHOW COLUMNS Statement"> <code class="literal"> SHOW COLUMNS </code> </a> statement to view additional information about the columns of this table, including data types and default values. </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/replication-administration-status.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="replication-administration-status"> </a> 19.1.7.1 Checking Replication Status </h4> </div> </div> </div> <p> The most common task when managing a replication process is to ensure that replication is taking place and that there have been no errors between the replica and the source. </p> <p> The <a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement"> <code class="literal"> SHOW REPLICA STATUS </code> </a> statement, which you must execute on each replica, provides information about the configuration and status of the connection between the replica server and the source server. The MySQL Performance Schema contains replication tables that provide this information in a more accessible form. See <a class="xref" href="performance-schema-replication-tables.html" title="29.12.11 Performance Schema Replication Tables"> Section 29.12.11, “Performance Schema Replication Tables” </a> . </p> <p> The replication heartbeat information shown in the Performance Schema replication tables lets you check that the replication connection is active even if the source has not sent events to the replica recently. The source sends a heartbeat signal to a replica if there are no updates to, and no unsent events in, the binary log for a longer period than the heartbeat interval. The <code class="literal"> SOURCE_HEARTBEAT_PERIOD </code> setting on the source (set by <a class="link" href="change-replication-source-to.html" title="15.4.2.2 CHANGE REPLICATION SOURCE TO Statement"> <code class="literal"> CHANGE REPLICATION SOURCE TO </code> </a> ) specifies the frequency of the heartbeat, which defaults to half of the connection timeout interval for the replica (specified by the system variable <a class="link" href="replication-options-replica.html#sysvar_replica_net_timeout"> <code class="literal"> replica_net_timeout </code> </a> . The <a class="link" href="performance-schema-replication-connection-status-table.html" title="29.12.11.13 The replication_connection_status Table"> <code class="literal"> replication_connection_status </code> </a> Performance Schema table shows when the most recent heartbeat signal was received by a replica, and how many heartbeat signals it has received. </p> <p> You can use <a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement"> <code class="literal"> SHOW REPLICA STATUS </code> </a> to check on the status of an individual replica; this statement provides the information shown here: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa50743417"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">REPLICA</span> <span class="token keyword">STATUS</span>\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Replica_IO_State<span class="token punctuation">:</span> Waiting for source to send event Source_Host<span class="token punctuation">:</span> 127.0.0.1 Source_User<span class="token punctuation">:</span> root Source_Port<span class="token punctuation">:</span> 13000 Connect_Retry<span class="token punctuation">:</span> 1 Source_Log_File<span class="token punctuation">:</span> master-bin.000001 Read_Source_Log_Pos<span class="token punctuation">:</span> 927 Relay_Log_File<span class="token punctuation">:</span> slave-relay-bin.000002 Relay_Log_Pos<span class="token punctuation">:</span> 1145 Relay_Source_Log_File<span class="token punctuation">:</span> master-bin.000001 Replica_IO_Running<span class="token punctuation">:</span> Yes Replica_SQL_Running<span class="token punctuation">:</span> Yes Replicate_Do_DB<span class="token punctuation">:</span> Replicate_Ignore_DB<span class="token punctuation">:</span> Replicate_Do_Table<span class="token punctuation">:</span> Replicate_Ignore_Table<span class="token punctuation">:</span> Replicate_Wild_Do_Table<span class="token punctuation">:</span> Replicate_Wild_Ignore_Table<span class="token punctuation">:</span> Last_Errno<span class="token punctuation">:</span> 0 Last_Error<span class="token punctuation">:</span> Skip_Counter<span class="token punctuation">:</span> 0 Exec_Source_Log_Pos<span class="token punctuation">:</span> 927 Relay_Log_Space<span class="token punctuation">:</span> 1355 Until_Condition<span class="token punctuation">:</span> None Until_Log_File<span class="token punctuation">:</span> Until_Log_Pos<span class="token punctuation">:</span> 0 Source_SSL_Allowed<span class="token punctuation">:</span> No Source_SSL_CA_File<span class="token punctuation">:</span> Source_SSL_CA_Path<span class="token punctuation">:</span> Source_SSL_Cert<span class="token punctuation">:</span> Source_SSL_Cipher<span class="token punctuation">:</span> Source_SSL_Key<span class="token punctuation">:</span> Seconds_Behind_Source<span class="token punctuation">:</span> 0 Source_SSL_Verify_Server_Cert<span class="token punctuation">:</span> No Last_IO_Errno<span class="token punctuation">:</span> 0 Last_IO_Error<span class="token punctuation">:</span> Last_SQL_Errno<span class="token punctuation">:</span> 0 Last_SQL_Error<span class="token punctuation">:</span> Replicate_Ignore_Server_Ids<span class="token punctuation">:</span> Source_Server_Id<span class="token punctuation">:</span> 1 Source_UUID<span class="token punctuation">:</span> 73f86016-978b-11ee-ade5-8d2a2a562feb Source_Info_File<span class="token punctuation">:</span> mysql.slave_master_info SQL_Delay<span class="token punctuation">:</span> 0 SQL_Remaining_Delay<span class="token punctuation">:</span> NULL Replica_SQL_Running_State<span class="token punctuation">:</span> Replica has read all relay log; waiting for more updates Source_Retry_Count<span class="token punctuation">:</span> 10 Source_Bind<span class="token punctuation">:</span> Last_IO_Error_Timestamp<span class="token punctuation">:</span> Last_SQL_Error_Timestamp<span class="token punctuation">:</span> Source_SSL_Crl<span class="token punctuation">:</span> Source_SSL_Crlpath<span class="token punctuation">:</span> Retrieved_Gtid_Set<span class="token punctuation">:</span> 73f86016-978b-11ee-ade5-8d2a2a562feb<span class="token punctuation">:</span>1-3 Executed_Gtid_Set<span class="token punctuation">:</span> 73f86016-978b-11ee-ade5-8d2a2a562feb<span class="token punctuation">:</span>1-3 Auto_Position<span class="token punctuation">:</span> 1 Replicate_Rewrite_DB<span class="token punctuation">:</span> Channel_Name<span class="token punctuation">:</span> Source_TLS_Version<span class="token punctuation">:</span> Source_public_key_path<span class="token punctuation">:</span> Get_Source_public_key<span class="token punctuation">:</span> 0 Network_Namespace<span class="token punctuation">:</span></span></code></pre> </div> <p> The key fields from the status report to examine are: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> Replica_IO_State </code> : The current status of the replica. See <a class="xref" href="replica-io-thread-states.html" title="10.14.5 Replication I/O (Receiver) Thread States"> Section 10.14.5, “Replication I/O (Receiver) Thread States” </a> , and <a class="xref" href="replica-sql-thread-states.html" title="10.14.6 Replication SQL Thread States"> Section 10.14.6, “Replication SQL Thread States” </a> , for more information. </p> </li> <li class="listitem"> <p> <code class="literal"> Replica_IO_Running </code> : Whether the I/O (receiver) thread for reading the source's binary log is running. Normally, you want this to be <code class="literal"> Yes </code> unless you have not yet started replication or have explicitly stopped it with <a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement"> <code class="literal"> STOP REPLICA </code> </a> . </p> </li> <li class="listitem"> <p> <code class="literal"> Replica_SQL_Running </code> : Whether the SQL thread for executing events in the relay log is running. As with the I/O thread, this should normally be <code class="literal"> Yes </code> . </p> </li> <li class="listitem"> <p> <code class="literal"> Last_IO_Error </code> , <code class="literal"> Last_SQL_Error </code> : The last errors registered by the I/O (receiver) and SQL (applier) threads when processing the relay log. Ideally these should be blank, indicating no errors. </p> </li> <li class="listitem"> <p> <code class="literal"> Seconds_Behind_Source </code> : The number of seconds that the replication SQL (applier) thread is behind processing the source binary log. A high number (or an increasing one) can indicate that the replica is unable to handle events from the source in a timely fashion. </p> <p> A value of 0 for <code class="literal"> Seconds_Behind_Source </code> can usually be interpreted as meaning that the replica has caught up with the source, but there are some cases where this is not strictly true. For example, this can occur if the network connection between source and replica is broken but the replication I/O (receiver) thread has not yet noticed this; that is, the time period set by <a class="link" href="replication-options-replica.html#sysvar_replica_net_timeout"> <code class="literal"> replica_net_timeout </code> </a> has not yet elapsed. </p> <p> It is also possible that transient values for <code class="literal"> Seconds_Behind_Source </code> may not reflect the situation accurately. When the replication SQL (applier) thread has caught up on I/O, <code class="literal"> Seconds_Behind_Source </code> displays 0; but when the replication I/O (receiver) thread is still queuing up a new event, <code class="literal"> Seconds_Behind_Source </code> may show a large value until the replication applier thread finishes executing the new event. This is especially likely when the events have old timestamps; in such cases, if you execute <a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement"> <code class="literal"> SHOW REPLICA STATUS </code> </a> several times in a relatively short period, you may see this value change back and forth repeatedly between 0 and a relatively large value. </p> </li> </ul> </div> <p> Several pairs of fields provide information about the progress of the replica in reading events from the source binary log and processing them in the relay log: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> ( <code class="literal"> Master_Log_file </code> , <code class="literal"> Read_Master_Log_Pos </code> ): Coordinates in the source binary log indicating how far the replication I/O (receiver) thread has read events from that log. </p> </li> <li class="listitem"> <p> ( <code class="literal"> Relay_Master_Log_File </code> , <code class="literal"> Exec_Master_Log_Pos </code> ): Coordinates in the source binary log indicating how far the replication SQL (applier) thread has executed events received from that log. </p> </li> <li class="listitem"> <p> ( <code class="literal"> Relay_Log_File </code> , <code class="literal"> Relay_Log_Pos </code> ): Coordinates in the replica relay log indicating how far the replication SQL (applier) thread has executed the relay log. These correspond to the preceding coordinates, but are expressed in replica relay log coordinates rather than source binary log coordinates. </p> </li> </ul> </div> <p> On the source, you can check the status of connected replicas using <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> to examine the list of running processes. Replica connections have <code class="literal"> Binlog Dump </code> in the <code class="literal"> Command </code> field: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa2643694"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">PROCESSLIST</span> \G<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 4. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Id<span class="token punctuation">:</span> 10 User<span class="token punctuation">:</span> root Host<span class="token punctuation">:</span> replica1<span class="token punctuation">:</span>58371 db<span class="token punctuation">:</span> NULL Command<span class="token punctuation">:</span> Binlog Dump Time<span class="token punctuation">:</span> 777 State<span class="token punctuation">:</span> Has sent all binlog to slave; waiting for binlog to be updated Info<span class="token punctuation">:</span> NULL</span></code></pre> </div> <p> Because it is the replica that drives the replication process, very little information is available in this report. </p> <p> For replicas that were started with the <a class="link" href="replication-options-replica.html#sysvar_report_host"> <code class="option"> --report-host </code> </a> option and are connected to the source, the <a class="link" href="show-replicas.html" title="15.7.7.36 SHOW REPLICAS Statement"> <code class="literal"> SHOW REPLICAS </code> </a> statement on the source shows basic information about the replicas. The output includes the ID of the replica server, the value of the <a class="link" href="replication-options-replica.html#sysvar_report_host"> <code class="option"> --report-host </code> </a> option, the connecting port, and source ID: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa35317527"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">REPLICAS</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> Server_id <span class="token punctuation">\|</span> Host <span class="token punctuation">\|</span> Port <span class="token punctuation">\|</span> Rpl_recovery_rank <span class="token punctuation">\|</span> Source_id <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 10 <span class="token punctuation">\|</span> replica1 <span class="token punctuation">\|</span> 3306 <span class="token punctuation">\|</span> 0 <span class="token punctuation">\|</span> 1 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/replication-privilege-checks-recover.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="replication-privilege-checks-recover"> </a> 19.3.3.3 Recovering From Failed Replication Privilege Checks </h4> </div> </div> </div> <p> If a privilege check against the <code class="literal"> PRIVILEGE_CHECKS_USER </code> account fails, the transaction is not executed and replication stops for the channel. Details of the error and the last applied transaction are recorded in the Performance Schema <a class="link" href="performance-schema-replication-applier-status-by-worker-table.html" title="29.12.11.7 The replication_applier_status_by_worker Table"> <code class="literal"> replication_applier_status_by_worker </code> </a> table. Follow this procedure to recover from the error: </p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p> Identify the replicated event that caused the error and verify whether or not the event is expected and from a trusted source. You can use <a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files"> <span class="command"> <strong> mysqlbinlog </strong> </span> </a> to retrieve and display the events that were logged around the time of the error. For instructions to do this, see <a class="xref" href="point-in-time-recovery.html" title="9.5 Point-in-Time (Incremental) Recovery"> Section 9.5, “Point-in-Time (Incremental) Recovery” </a> . </p> </li> <li class="listitem"> <p> If the replicated event is not expected or is not from a known and trusted source, investigate the cause. If you can identify why the event took place and there are no security considerations, proceed to fix the error as described below. </p> </li> <li class="listitem"> <p> If the <code class="literal"> PRIVILEGE_CHECKS_USER </code> account should have been permitted to execute the transaction, but has been misconfigured, grant the missing privileges to the account, use a <a class="link" href="flush.html#flush-privileges"> <code class="literal"> FLUSH PRIVILEGES </code> </a> statement or execute a <a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program"> <span class="command"> <strong> mysqladmin flush-privileges </strong> </span> </a> or <a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program"> <span class="command"> <strong> mysqladmin reload </strong> </span> </a> command to reload the grant tables, then restart replication for the channel. </p> </li> <li class="listitem"> <p> If the transaction needs to be executed and you have verified that it is trusted, but the <code class="literal"> PRIVILEGE_CHECKS_USER </code> account should not have this privilege normally, you can grant the required privilege to the <code class="literal"> PRIVILEGE_CHECKS_USER </code> account temporarily. After the replicated event has been applied, remove the privilege from the account, and take any necessary steps to ensure the event does not recur if it is avoidable. </p> </li> <li class="listitem"> <p> If the transaction is an administrative action that should only have taken place on the source and not on the replica, or should only have taken place on a single replication group member, skip the transaction on the server or servers where it stopped replication, then issue <a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement"> <code class="literal"> START REPLICA </code> </a> to restart replication on the channel. To avoid the situation in future, you could issue such administrative statements with <code class="literal"> SET sql_log_bin = 0 </code> before them and <code class="literal"> SET sql_log_bin = 1 </code> after them, so that they are not logged on the source. </p> </li> <li class="listitem"> <p> If the transaction is a DDL or DML statement that should not have taken place on either the source or the replica, skip the transaction on the server or servers where it stopped replication, undo the transaction manually on the server where it originally took place, then issue <a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement"> <code class="literal"> START REPLICA </code> </a> to restart replication. </p> </li> </ol> </div> <p> To skip a transaction, if GTIDs are in use, commit an empty transaction that has the GTID of the failing transaction, for example: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa35036198"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> GTID_NEXT<span class="token operator">=</span><span class="token string">'aaa-bbb-ccc-ddd:N'</span><span class="token punctuation">;</span> <span class="token keyword">BEGIN</span><span class="token punctuation">;</span> <span class="token keyword">COMMIT</span><span class="token punctuation">;</span> <span class="token keyword">SET</span> GTID_NEXT<span class="token operator">=</span><span class="token string">'AUTOMATIC'</span><span class="token punctuation">;</span></code></pre> </div> <p> If GTIDs are not in use, issue a <code class="literal"> SET GLOBAL sql_replica_skip_counter </code> statement to skip the event. For instructions to use this alternative method and more details about skipping transactions, see <a class="xref" href="replication-administration-skip.html" title="19.1.7.3 Skipping Transactions"> Section 19.1.7.3, “Skipping Transactions” </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/group-replication-single-primary-mode.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="group-replication-single-primary-mode"> </a> 20.1.3.1 Single-Primary Mode </h4> </div> </div> </div> <a class="indexterm" name="idm46045134489696"> </a> <a class="indexterm" name="idm46045134488208"> </a> <p> In single-primary mode ( <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_single_primary_mode"> <code class="literal"> group_replication_single_primary_mode=ON </code> </a> ) the group has a single primary server that is set to read/write mode. All the other members in the group are set to read-only mode (with <a class="link" href="server-system-variables.html#sysvar_super_read_only"> <code class="literal"> super_read_only=ON </code> </a> ). The primary typically bootstraps the entire group. All other servers that join the group learn about the primary server and are automatically set to read-only mode. </p> <p> In single-primary mode, Group Replication enforces that only a single server writes to the group, so compared to multi-primary mode, consistency checking can be less strict and DDL statements do not need to be handled with any extra care. The option <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_enforce_update_everywhere_checks"> <code class="literal"> group_replication_enforce_update_everywhere_checks </code> </a> enables or disables strict consistency checks for a group. When deploying in single-primary mode, or changing the group to single-primary mode, this system variable must be set to <code class="literal"> OFF </code> . </p> <p> The member that is designated as the primary server can change in the following ways: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> If the existing primary leaves the group, whether voluntarily or unexpectedly, a new primary is elected automatically. </p> </li> <li class="listitem"> <p> You can appoint a specific member as the new primary using the <a class="link" href="group-replication-functions-for-new-primary.html#function_group-replication-set-as-primary"> <code class="literal"> group_replication_set_as_primary() </code> </a> function. </p> </li> <li class="listitem"> <p> If you use the <a class="link" href="group-replication-functions-for-mode.html#function_group-replication-switch-to-single-primary-mode"> <code class="literal"> group_replication_switch_to_single_primary_mode() </code> </a> function to change a group that was running in multi-primary mode to run in single-primary mode, a new primary is elected automatically, or you can appoint the new primary by specifying it with the function. </p> </li> </ul> </div> <p> When a new primary server is elected (automatically or manually), it is automatically set to read/write, and the other group members remain as secondaries, and as such, read-only. The following diagram shows this process: </p> <div class="figure"> <a name="group-replication-primary-election-diagram"> </a> <p class="title"> <b> Figure 20.4 New Primary Election </b> </p> <div class="figure-contents"> <div class="mediaobject"> <img alt="Five server instances, S1, S2, S3, S4, and S5, are deployed as an interconnected group. Server S1 is the primary. Write clients are communicating with server S1, and a read client is communicating with server S4. Server S1 then fails, breaking communication with the write clients. Server S2 then takes over as the new primary, and the write clients now communicate with server S2." src="images/single-primary-election.png" style="width: 100%; max-width: 899px;"/> </div> </div> </div> <br class="figure-break"/> <p> When a new primary is chosen, it might have a backlog of changes that had been applied on the old primary but have not yet been applied on the new one. In this case, until the new primary catches up with the old one, read/write transactions might result in conflicts and be rolled back, and read-only transactions might result in stale reads. The Group Replication flow control mechanism minimizes the difference between fast and slow members, and so reduces the chances of this happening if it is activated and properly tuned. For more information, see <a class="xref" href="group-replication-flow-control.html" title="20.7.2 Flow Control"> Section 20.7.2, “Flow Control” </a> . You can also use the <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_consistency"> <code class="literal"> group_replication_consistency </code> </a> system variable to set the group's level of transaction consistency to prevent this issue. Setting this variable to <code class="literal"> BEFORE_ON_PRIMARY_FAILOVER </code> (the default) or any higher consistency level holds new transactions on a newly elected primary until the backlog has been applied. </p> <p> For more information on transaction consistency, see <a class="xref" href="group-replication-consistency-guarantees.html" title="20.5.3 Transaction Consistency Guarantees"> Section 20.5.3, “Transaction Consistency Guarantees” </a> . If flow control and transaction consistency guarantees are not used for a group, it is a good practice to wait for the new primary to apply its replication-related relay log before re-routing client applications to it. </p> <div class="section"> <div class="titlepage"> <div> <div> <h5 class="title"> <a name="group-replication-primary-election"> </a> 20.1.3.1.1 Primary Election Algorithm </h5> </div> </div> </div> <p> The automatic primary member election process involves each member looking at the new view of the group, ordering the potential new primary members, and choosing the member that qualifies as the most suitable. Each member makes its own decision locally, following the primary election algorithm in its MySQL Server release. Because all members must reach the same decision, members adapt their primary election algorithm if other group members are running lower MySQL Server versions, so that they have the same behavior as the member with the lowest MySQL Server version in the group. </p> <p> The factors considered by members when electing a primary, in order, are as follows: </p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p> The first factor considered is which member or members are running the lowest MySQL Server version. All group members are first ordered by the patch version of their release. </p> </li> <li class="listitem"> <p> If more than one member is running the lowest MySQL Server version, the second factor considered is the member weight of each of those members, as specified by the <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_member_weight"> <code class="literal"> group_replication_member_weight </code> </a> system variable on the member. </p> <p> The <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_member_weight"> <code class="literal"> group_replication_member_weight </code> </a> system variable specifies a number in the range 0-100. All members default to a weight of 50, so set a weight below this to lower their ordering, and a weight above it to increase their ordering. You can use this weighting function to prioritize the use of better hardware or to ensure failover to a specific member during scheduled maintenance of the primary. </p> </li> <li class="listitem"> <p> If more than one member is running the lowest MySQL Server version, and more than one of those members has the highest member weight (or member weighting is being ignored), the third factor considered is the lexicographical order of the generated server UUIDs of each member, as specified by the <a class="link" href="replication-options.html#sysvar_server_uuid"> <code class="literal"> server_uuid </code> </a> system variable. The member with the lowest server UUID is chosen as the primary. This factor acts as a guaranteed and predictable tie-breaker so that all group members reach the same decision if it cannot be determined by any important factors. </p> </li> </ol> </div> <p> </p> </div> <div class="section"> <div class="titlepage"> <div> <div> <h5 class="title"> <a name="group-replication-find-primary"> </a> 20.1.3.1.2 Finding the Primary </h5> </div> </div> </div> <a class="indexterm" name="idm46045134447520"> </a> <p> To find out which server is currently the primary when deployed in single-primary mode, use the <code class="literal"> MEMBER_ROLE </code> column in the <a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table"> <code class="literal"> performance_schema.replication_group_members </code> </a> table. For example: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa42339057"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> MEMBER_HOST<span class="token punctuation">,</span> MEMBER_ROLE <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> MEMBER_HOST <span class="token punctuation">\|</span> MEMBER_ROLE <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> remote1.example.com <span class="token punctuation">\|</span> PRIMARY <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> remote2.example.com <span class="token punctuation">\|</span> SECONDARY <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> remote3.example.com <span class="token punctuation">\|</span> SECONDARY <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/fulltext-query-expansion.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="fulltext-query-expansion"> </a> 14.9.3 Full-Text Searches with Query Expansion </h3> </div> </div> </div> <a class="indexterm" name="idm46045201620208"> </a> <a class="indexterm" name="idm46045201619136"> </a> <p> Full-text search supports query expansion (and in particular, its variant <span class="quote"> “ <span class="quote"> blind query expansion </span> ” </span> ). This is generally useful when a search phrase is too short, which often means that the user is relying on implied knowledge that the full-text search engine lacks. For example, a user searching for <span class="quote"> “ <span class="quote"> database </span> ” </span> may really mean that <span class="quote"> “ <span class="quote"> MySQL </span> ” </span> , <span class="quote"> “ <span class="quote"> Oracle </span> ” </span> , <span class="quote"> “ <span class="quote"> DB2 </span> ” </span> , and <span class="quote"> “ <span class="quote"> RDBMS </span> ” </span> all are phrases that should match <span class="quote"> “ <span class="quote"> databases </span> ” </span> and should be returned, too. This is implied knowledge. </p> <p> Blind query expansion (also known as automatic relevance feedback) is enabled by adding <code class="literal"> WITH QUERY EXPANSION </code> or <code class="literal"> IN NATURAL LANGUAGE MODE WITH QUERY EXPANSION </code> following the search phrase. It works by performing the search twice, where the search phrase for the second search is the original search phrase concatenated with the few most highly relevant documents from the first search. Thus, if one of these documents contains the word <span class="quote"> “ <span class="quote"> databases </span> ” </span> and the word <span class="quote"> “ <span class="quote"> MySQL </span> ” </span> , the second search finds the documents that contain the word <span class="quote"> “ <span class="quote"> MySQL </span> ” </span> even if they do not contain the word <span class="quote"> “ <span class="quote"> database </span> ” </span> . The following example shows this difference: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa9375064"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> articles <span class="token keyword">WHERE</span> <span class="token operator">MATCH</span> <span class="token punctuation">(</span>title<span class="token punctuation">,</span>body<span class="token punctuation">)</span> <span class="token keyword">AGAINST</span> <span class="token punctuation">(</span><span class="token string">'database'</span> <span class="token keyword">IN</span> <span class="token keyword">NATURAL</span> <span class="token keyword">LANGUAGE</span> <span class="token keyword">MODE</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> id <span class="token punctuation">\|</span> title <span class="token punctuation">\|</span> body <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token 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punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 1 <span class="token punctuation">\|</span> MySQL Tutorial <span class="token punctuation">\|</span> DBMS stands for DataBase ... <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> 5 <span class="token punctuation">\|</span> MySQL vs. YourSQL <span class="token punctuation">\|</span> In the following database comparison ... <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token 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keyword">EXPANSION</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token 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punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> id <span class="token punctuation">\|</span> title <span class="token punctuation">\|</span> body <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span 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class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 5 <span class="token punctuation">\|</span> MySQL vs. YourSQL <span class="token punctuation">\|</span> In the following database comparison ... <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> 1 <span class="token punctuation">\|</span> MySQL Tutorial <span class="token punctuation">\|</span> DBMS stands for DataBase ... <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> 3 <span class="token punctuation">\|</span> Optimizing MySQL <span class="token punctuation">\|</span> In this tutorial we show ... <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> 6 <span class="token punctuation">\|</span> MySQL Security <span class="token punctuation">\|</span> When configured properly, MySQL ... <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> 2 <span class="token punctuation">\|</span> How To Use MySQL Well <span class="token punctuation">\|</span> After you went through a ... <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> 4 <span class="token punctuation">\|</span> 1001 MySQL Tricks <span class="token punctuation">\|</span> 1. Never run mysqld as root. 2. ... <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">6 rows in set (0.00 sec)</span></code></pre> </div> <p> Another example could be searching for books by Georges Simenon about Maigret, when a user is not sure how to spell <span class="quote"> “ <span class="quote"> Maigret </span> ” </span> . A search for <span class="quote"> “ <span class="quote"> Megre and the reluctant witnesses </span> ” </span> finds only <span class="quote"> “ <span class="quote"> Maigret and the Reluctant Witnesses </span> ” </span> without query expansion. A search with query expansion finds all books with the word <span class="quote"> “ <span class="quote"> Maigret </span> ” </span> on the second pass. </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> Because blind query expansion tends to increase noise significantly by returning nonrelevant documents, use it only when a search phrase is short. </p> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-rolling-restart.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="mysql-cluster-rolling-restart"> </a> 25.6.5 Performing a Rolling Restart of an NDB Cluster </h3> </div> </div> </div> <a class="indexterm" name="idm46045092605824"> </a> <a class="indexterm" name="idm46045092604336"> </a> <a class="indexterm" name="idm46045092603232"> </a> <a class="indexterm" name="idm46045092601744"> </a> <a class="indexterm" name="idm46045092600256"> </a> <p> This section discusses how to perform a <span class="firstterm"> rolling restart </span> of an NDB Cluster installation, so called because it involves stopping and starting (or restarting) each node in turn, so that the cluster itself remains operational. This is often done as part of a <span class="firstterm"> rolling upgrade </span> or <span class="firstterm"> rolling downgrade </span> , where high availability of the cluster is mandatory and no downtime of the cluster as a whole is permissible. Where we refer to upgrades, the information provided here also generally applies to downgrades as well. </p> <p> There are a number of reasons why a rolling restart might be desirable. These are described in the next few paragraphs. </p> <p> <b> Configuration change. </b> <a class="indexterm" name="idm46045092594960"> </a> To make a change in the cluster's configuration, such as adding an SQL node to the cluster, or setting a configuration parameter to a new value. </p> <p> <b> NDB Cluster software upgrade or downgrade. </b> To upgrade the cluster to a newer version of the NDB Cluster software (or to downgrade it to an older version). This is usually referred to as a <span class="quote"> “ <span class="quote"> rolling upgrade </span> ” </span> (or <span class="quote"> “ <span class="quote"> rolling downgrade </span> ” </span> , when reverting to an older version of NDB Cluster). </p> <p> <b> Change on node host. </b> To make changes in the hardware or operating system on which one or more NDB Cluster node processes are running. </p> <p> <b> System reset (cluster reset). </b> <a class="indexterm" name="idm46045092588384"> </a> To reset the cluster because it has reached an undesirable state. In such cases it is often desirable to reload the data and metadata of one or more data nodes. This can be done in any of three ways: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> Start each data node process ( <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> <span class="command"> <strong> ndbd </strong> </span> </a> or possibly <a class="link" href="mysql-cluster-programs-ndbmtd.html" title="25.5.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)"> <span class="command"> <strong> ndbmtd </strong> </span> </a> ) with the <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_initial"> <code class="option"> --initial </code> </a> option, which forces the data node to clear its file system and to reload all NDB Cluster data and metadata from the other data nodes. This also forces the removal of all Disk Data objects and files associated with those objects. </p> </li> <li class="listitem"> <p> Create a backup using the <a class="link" href="mysql-cluster-programs-ndb-mgm.html" title="25.5.5 ndb_mgm — The NDB Cluster Management Client"> <span class="command"> <strong> ndb_mgm </strong> </span> </a> client <a class="link" href="mysql-cluster-backup-using-management-client.html" title="25.6.8.2 Using The NDB Cluster Management Client to Create a Backup"> <code class="literal"> START BACKUP </code> </a> command prior to performing the restart. Following the upgrade, restore the node or nodes using <a class="link" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup"> <span class="command"> <strong> ndb_restore </strong> </span> </a> . </p> <p> See <a class="xref" href="mysql-cluster-backup.html" title="25.6.8 Online Backup of NDB Cluster"> Section 25.6.8, “Online Backup of NDB Cluster” </a> , and <a class="xref" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup"> Section 25.5.23, “ndb_restore — Restore an NDB Cluster Backup” </a> , for more information. </p> </li> <li class="listitem"> <p> Use <a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program"> <span class="command"> <strong> mysqldump </strong> </span> </a> to create a backup prior to the upgrade; afterward, restore the dump using <a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement"> <code class="literal"> LOAD DATA </code> </a> . </p> </li> </ul> </div> <p> <b> Resource Recovery. </b> <a class="indexterm" name="idm46045092570592"> </a> To free memory previously allocated to a table by successive <a class="link" href="insert.html" title="15.2.7 INSERT Statement"> <code class="literal"> INSERT </code> </a> and <a class="link" href="delete.html" title="15.2.2 DELETE Statement"> <code class="literal"> DELETE </code> </a> operations, for re-use by other NDB Cluster tables. </p> <p> The process for performing a rolling restart may be generalized as follows: </p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p> Stop all cluster management nodes ( <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> processes), reconfigure them, then restart them. (See <a class="xref" href="mysql-cluster-rolling-restart.html#mysql-cluster-rolling-restart-multiple-ndb-mgmd" title="Rolling restarts with multiple management servers"> Rolling restarts with multiple management servers </a> .) </p> </li> <li class="listitem"> <p> Stop, reconfigure, then restart each cluster data node ( <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> <span class="command"> <strong> ndbd </strong> </span> </a> process) in turn. </p> <p> Some node configuration parameters can be updated by issuing <a class="link" href="mysql-cluster-mgm-client-commands.html#ndbclient-restart"> <code class="literal"> RESTART </code> </a> for each of the data nodes in the <a class="link" href="mysql-cluster-programs-ndb-mgm.html" title="25.5.5 ndb_mgm — The NDB Cluster Management Client"> <span class="command"> <strong> ndb_mgm </strong> </span> </a> client following the previous step. Other parameters require that the data node be stopped completely using the management client <a class="link" href="mysql-cluster-mgm-client-commands.html#ndbclient-stop"> <code class="literal"> STOP </code> </a> command, then started again from a system shell by invoking the <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> <span class="command"> <strong> ndbd </strong> </span> </a> or <a class="link" href="mysql-cluster-programs-ndbmtd.html" title="25.5.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)"> <span class="command"> <strong> ndbmtd </strong> </span> </a> executable as appropriate. (A shell command such as <a class="link" href="kill.html" title="15.7.8.4 KILL Statement"> <span class="command"> <strong> kill </strong> </span> </a> can also be used on most Unix systems to stop a data node process, but the <code class="literal"> STOP </code> command is preferred and usually simpler.) </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> On Windows, you can also use <span class="command"> <strong> SC STOP </strong> </span> and <span class="command"> <strong> SC START </strong> </span> commands, <code class="literal"> NET STOP </code> and <code class="literal"> NET START </code> commands, or the Windows Service Manager to stop and start nodes which have been installed as Windows services (see <a class="xref" href="mysql-cluster-install-windows-service.html" title="25.3.2.4 Installing NDB Cluster Processes as Windows Services"> Section 25.3.2.4, “Installing NDB Cluster Processes as Windows Services” </a> ). </p> </div> <p> The type of restart required is indicated in the documentation for each node configuration parameter. See <a class="xref" href="mysql-cluster-config-file.html" title="25.4.3 NDB Cluster Configuration Files"> Section 25.4.3, “NDB Cluster Configuration Files” </a> . </p> </li> <li class="listitem"> <p> Stop, reconfigure, then restart each cluster SQL node ( <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server"> <span class="command"> <strong> mysqld </strong> </span> </a> process) in turn. </p> </li> </ol> </div> <a class="indexterm" name="idm46045092542352"> </a> <p> NDB Cluster supports a somewhat flexible order for upgrading nodes. When upgrading an NDB Cluster, you may upgrade API nodes (including SQL nodes) before upgrading the management nodes, data nodes, or both. In other words, you are permitted to upgrade the API and SQL nodes in any order. This is subject to the following provisions: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> This functionality is intended for use as part of an online upgrade only. A mix of node binaries from different NDB Cluster releases is neither intended nor supported for continuous, long-term use in a production setting. </p> </li> <li class="listitem"> <p> You must upgrade all nodes of the same type (management, data, or API node) before upgrading any nodes of a different type. This remains true regardless of the order in which the nodes are upgraded. </p> </li> <li class="listitem"> <p> You must upgrade all management nodes before upgrading any data nodes. This remains true regardless of the order in which you upgrade the cluster's API and SQL nodes. </p> </li> <li class="listitem"> <p> Features specific to the <span class="quote"> “ <span class="quote"> new </span> ” </span> version must not be used until all management nodes and data nodes have been upgraded. </p> <p> This also applies to any MySQL Server version change that may apply, in addition to the NDB engine version change, so do not forget to take this into account when planning the upgrade. (This is true for online upgrades of NDB Cluster in general.) </p> </li> </ul> </div> <p> It is not possible for any API node to perform schema operations (such as data definition statements) during a node restart. Due in part to this limitation, schema operations are also not supported during an online upgrade or downgrade. In addition, it is not possible to perform native backups while an upgrade or downgrade is ongoing. </p> <p> <a name="mysql-cluster-rolling-restart-multiple-ndb-mgmd"> </a> <b> Rolling restarts with multiple management servers. </b> <a class="indexterm" name="idm46045092532384"> </a> <a class="indexterm" name="idm46045092530864"> </a> When performing a rolling restart of an NDB Cluster with multiple management nodes, you should keep in mind that <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> checks to see if any other management node is running, and, if so, tries to use that node's configuration data. To keep this from occurring, and to force <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> to re-read its configuration file, perform the following steps: </p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p> Stop all NDB Cluster <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> processes. </p> </li> <li class="listitem"> <p> Update all <code class="filename"> config.ini </code> files. </p> </li> <li class="listitem"> <p> Start a single <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> with <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_reload"> <code class="option"> --reload </code> </a> , <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_initial"> <code class="option"> --initial </code> </a> , or both options as desired. </p> </li> <li class="listitem"> <p> If you started the first <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> with the <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_initial"> <code class="option"> --initial </code> </a> option, you must also start any remaining <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> processes using <code class="option"> --initial </code> . </p> <p> Regardless of any other options used when starting the first <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> , you should not start any remaining <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> processes after the first one using <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_reload"> <code class="option"> --reload </code> </a> . </p> </li> <li class="listitem"> <p> Complete the rolling restarts of the data nodes and API nodes as normal. </p> </li> </ol> </div> <p> When performing a rolling restart to update the cluster's configuration, you can use the <code class="literal"> config_generation </code> column of the <a class="link" href="mysql-cluster-ndbinfo-nodes.html" title="25.6.17.48 The ndbinfo nodes Table"> <code class="literal"> ndbinfo.nodes </code> </a> table to keep track of which data nodes have been successfully restarted with the new configuration. See <a class="xref" href="mysql-cluster-ndbinfo-nodes.html" title="25.6.17.48 The ndbinfo nodes Table"> Section 25.6.17.48, “The ndbinfo nodes Table” </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/sys-latest-file-io.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="sys-latest-file-io"> </a> 30.4.3.15 The latest_file_io and x$latest_file_io Views </h4> </div> </div> </div> <a class="indexterm" name="idm46045062894000"> </a> <a class="indexterm" name="idm46045062892544"> </a> <a class="indexterm" name="idm46045062891056"> </a> <a class="indexterm" name="idm46045062889568"> </a> <p> These views summarize file I/O activity, grouped by file and thread. By default, rows are sorted with most recent I/O first. </p> <p> The <a class="link" href="sys-latest-file-io.html" title="30.4.3.15 The latest_file_io and x$latest_file_io Views"> <code class="literal"> latest_file_io </code> </a> and <a class="link" href="sys-latest-file-io.html" title="30.4.3.15 The latest_file_io and x$latest_file_io Views"> <code class="literal"> x$latest_file_io </code> </a> views have these columns: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> thread </code> </p> <p> For foreground threads, the account associated with the thread (and port number for TCP/IP connections). For background threads, the thread name and thread ID </p> </li> <li class="listitem"> <p> <code class="literal"> file </code> </p> <p> The file path name. </p> </li> <li class="listitem"> <p> <code class="literal"> latency </code> </p> <p> The wait time of the file I/O event. </p> </li> <li class="listitem"> <p> <code class="literal"> operation </code> </p> <p> The type of operation. </p> </li> <li class="listitem"> <p> <code class="literal"> requested </code> </p> <p> The number of data bytes requested for the file I/O event. </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/create-logfile-group.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="create-logfile-group"> </a> 15.1.16 CREATE LOGFILE GROUP Statement </h3> </div> </div> </div> <a class="indexterm" name="idm46045187348880"> </a> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63712911"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">LOGFILE</span> <span class="token keyword">GROUP</span> <em class="replaceable">logfile_group</em> <span class="token keyword">ADD</span> <span class="token keyword">UNDOFILE</span> <span class="token string">'<em class="replaceable">undo_file</em>'</span> <span class="token punctuation">[</span><span class="token keyword">INITIAL_SIZE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">initial_size</em></span><span class="token punctuation">]</span> <span class="token punctuation">[</span><span class="token keyword">UNDO_BUFFER_SIZE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">undo_buffer_size</em></span><span class="token punctuation">]</span> <span class="token punctuation">[</span><span class="token keyword">REDO_BUFFER_SIZE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">redo_buffer_size</em></span><span class="token punctuation">]</span> <span class="token punctuation">[</span><span class="token keyword">NODEGROUP</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">nodegroup_id</em><span class="token punctuation">]</span> <span class="token punctuation">[</span><span class="token keyword">WAIT</span><span class="token punctuation">]</span> <span class="token punctuation">[</span><span class="token keyword">COMMENT</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token string">'<em class="replaceable">string</em>'</span><span class="token punctuation">]</span> <span class="token keyword">ENGINE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">engine_name</em></code></pre> </div> <p> This statement creates a new log file group named <em class="replaceable"> <code> logfile_group </code> </em> having a single undo file named ' <em class="replaceable"> <code> undo_file </code> </em> '. A <a class="link" href="create-logfile-group.html" title="15.1.16 CREATE LOGFILE GROUP Statement"> <code class="literal"> CREATE LOGFILE GROUP </code> </a> statement has one and only one <code class="literal"> ADD UNDOFILE </code> clause. For rules covering the naming of log file groups, see <a class="xref" href="identifiers.html" title="11.2 Schema Object Names"> Section 11.2, “Schema Object Names” </a> . </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> All NDB Cluster Disk Data objects share the same namespace. This means that <span class="emphasis"> <em> each Disk Data object </em> </span> must be uniquely named (and not merely each Disk Data object of a given type). For example, you cannot have a tablespace and a log file group with the same name, or a tablespace and a data file with the same name. </p> </div> <p> There can be only one log file group per NDB Cluster instance at any given time. </p> <p> The optional <code class="literal"> INITIAL_SIZE </code> parameter sets the undo file's initial size; if not specified, it defaults to <code class="literal"> 128M </code> (128 megabytes). The optional <code class="literal"> UNDO_BUFFER_SIZE </code> parameter sets the size used by the undo buffer for the log file group; The default value for <code class="literal"> UNDO_BUFFER_SIZE </code> is <code class="literal"> 8M </code> (eight megabytes); this value cannot exceed the amount of system memory available. Both of these parameters are specified in bytes. You may optionally follow either or both of these with a one-letter abbreviation for an order of magnitude, similar to those used in <code class="filename"> my.cnf </code> . Generally, this is one of the letters <code class="literal"> M </code> (for megabytes) or <code class="literal"> G </code> (for gigabytes). </p> <p> Memory used for <code class="literal"> UNDO_BUFFER_SIZE </code> comes from the global pool whose size is determined by the value of the <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-sharedglobalmemory"> <code class="literal"> SharedGlobalMemory </code> </a> data node configuration parameter. This includes any default value implied for this option by the setting of the <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-initiallogfilegroup"> <code class="literal"> InitialLogFileGroup </code> </a> data node configuration parameter. </p> <p> The maximum permitted for <code class="literal"> UNDO_BUFFER_SIZE </code> is 629145600 (600 MB). </p> <p> On 32-bit systems, the maximum supported value for <code class="literal"> INITIAL_SIZE </code> is 4294967296 (4 GB). (Bug #29186) </p> <p> The minimum allowed value for <code class="literal"> INITIAL_SIZE </code> is 1048576 (1 MB). </p> <p> The <code class="literal"> ENGINE </code> option determines the storage engine to be used by this log file group, with <em class="replaceable"> <code> engine_name </code> </em> being the name of the storage engine. This must be <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> (or <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDBCLUSTER </code> </a> ). If <code class="literal"> ENGINE </code> is not set, MySQL tries to use the engine specified by the <a class="link" href="server-system-variables.html#sysvar_default_storage_engine"> <code class="literal"> default_storage_engine </code> </a> server system variable. In any case, if the engine is not specified as <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> or <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDBCLUSTER </code> </a> , the <code class="literal"> CREATE LOGFILE GROUP </code> statement appears to succeed but actually fails to create the log file group, as shown here: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa364070"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">LOGFILE</span> <span class="token keyword">GROUP</span> lg1 <span class="token prompt"> -></span> <span class="token keyword">ADD</span> <span class="token keyword">UNDOFILE</span> <span class="token string">'undo.dat'</span> <span class="token keyword">INITIAL_SIZE</span> <span class="token operator">=</span> 10M<span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected, 1 warning (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">WARNINGS</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token 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punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> Level <span class="token punctuation">\|</span> Code <span class="token punctuation">\|</span> Message <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token 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punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> Error <span class="token punctuation">\|</span> 1478 <span class="token punctuation">\|</span> Table storage engine 'InnoDB' does not support the create option 'TABLESPACE or LOGFILE GROUP' <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">DROP</span> <span class="token keyword">LOGFILE</span> <span class="token keyword">GROUP</span> lg1 <span class="token keyword">ENGINE</span> <span class="token operator">=</span> <span class="token keyword">NDB</span><span class="token punctuation">;</span> <span class="token output">ERROR 1529 (HY000)<span class="token punctuation">:</span> Failed to drop LOGFILE GROUP </span> <span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">LOGFILE</span> <span class="token keyword">GROUP</span> lg1 <span class="token prompt"> -></span> <span class="token keyword">ADD</span> <span class="token keyword">UNDOFILE</span> <span class="token string">'undo.dat'</span> <span class="token keyword">INITIAL_SIZE</span> <span class="token operator">=</span> 10M <span class="token prompt"> -></span> <span class="token keyword">ENGINE</span> <span class="token operator">=</span> <span class="token keyword">NDB</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (2.97 sec)</span></code></pre> </div> <p> The fact that the <code class="literal"> CREATE LOGFILE GROUP </code> statement does not actually return an error when a storage engine other than <code class="literal"> NDB </code> is specified, but rather appears to succeed, is a known issue which we hope to address in a future version of NDB Cluster. </p> <p> <em class="replaceable"> <code> REDO_BUFFER_SIZE </code> </em> , <code class="literal"> NODEGROUP </code> , <code class="literal"> WAIT </code> , and <code class="literal"> COMMENT </code> are parsed but ignored, and so have no effect in MySQL 8.4. These options are intended for future expansion. </p> <p> When used with <code class="literal"> ENGINE [=] NDB </code> , a log file group and associated undo log file are created on each Cluster data node. You can verify that the undo files were created and obtain information about them by querying the Information Schema <a class="link" href="information-schema-files-table.html" title="28.3.15 The INFORMATION_SCHEMA FILES Table"> <code class="literal"> FILES </code> </a> table. For example: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47575318"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> LOGFILE_GROUP_NAME<span class="token punctuation">,</span> LOGFILE_GROUP_NUMBER<span class="token punctuation">,</span> EXTRA <span class="token prompt"> -></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>FILES <span class="token prompt"> -></span> <span class="token keyword">WHERE</span> FILE_NAME <span class="token operator">=</span> <span class="token string">'undo_10.dat'</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> LOGFILE_GROUP_NAME <span class="token punctuation">\|</span> LOGFILE_GROUP_NUMBER <span class="token punctuation">\|</span> EXTRA <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> lg_3 <span class="token punctuation">\|</span> 11 <span class="token punctuation">\|</span> CLUSTER_NODE=3 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> lg_3 <span class="token punctuation">\|</span> 11 <span class="token punctuation">\|</span> CLUSTER_NODE=4 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">2 rows in set (0.06 sec)</span></code></pre> </div> <p> <a class="link" href="create-logfile-group.html" title="15.1.16 CREATE LOGFILE GROUP Statement"> <code class="literal"> CREATE LOGFILE GROUP </code> </a> is useful only with Disk Data storage for NDB Cluster. See <a class="xref" href="mysql-cluster-disk-data.html" title="25.6.11 NDB Cluster Disk Data Tables"> Section 25.6.11, “NDB Cluster Disk Data Tables” </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/optimize-blob.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="optimize-blob"> </a> 10.4.2.3 Optimizing for BLOB Types </h4> </div> </div> </div> <a class="indexterm" name="idm46045226748016"> </a> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> When storing a large blob containing textual data, consider compressing it first. Do not use this technique when the entire table is compressed by <code class="literal"> InnoDB </code> or <code class="literal"> MyISAM </code> . </p> </li> <li class="listitem"> <p> For a table with several columns, to reduce memory requirements for queries that do not use the BLOB column, consider splitting the BLOB column into a separate table and referencing it with a join query when needed. </p> </li> <li class="listitem"> <p> Since the performance requirements to retrieve and display a BLOB value might be very different from other data types, you could put the BLOB-specific table on a different storage device or even a separate database instance. For example, to retrieve a BLOB might require a large sequential disk read that is better suited to a traditional hard drive than to an <a class="link" href="glossary.html#glos_ssd" title="SSD"> SSD device </a> . </p> </li> <li class="listitem"> <p> See <a class="xref" href="optimize-character.html" title="10.4.2.2 Optimizing for Character and String Types"> Section 10.4.2.2, “Optimizing for Character and String Types” </a> for reasons why a binary <code class="literal"> VARCHAR </code> column is sometimes preferable to an equivalent BLOB column. </p> </li> <li class="listitem"> <p> Rather than testing for equality against a very long text string, you can store a hash of the column value in a separate column, index that column, and test the hashed value in queries. (Use the <code class="literal"> MD5() </code> or <code class="literal"> CRC32() </code> function to produce the hash value.) Since hash functions can produce duplicate results for different inputs, you still include a clause <code class="literal"> AND <em class="replaceable"> <code> blob_column </code> </em> = <em class="replaceable"> <code> long_string_value </code> </em> </code> in the query to guard against false matches; the performance benefit comes from the smaller, easily scanned index for the hashed values. </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/describe.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="describe"> </a> 15.8.1 DESCRIBE Statement </h3> </div> </div> </div> <a class="indexterm" name="idm46045168208224"> </a> <a class="indexterm" name="idm46045168207152"> </a> <p> The <a class="link" href="describe.html" title="15.8.1 DESCRIBE Statement"> <code class="literal"> DESCRIBE </code> </a> and <a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement"> <code class="literal"> EXPLAIN </code> </a> statements are synonyms, used either to obtain information about table structure or query execution plans. For more information, see <a class="xref" href="show-columns.html" title="15.7.7.6 SHOW COLUMNS Statement"> Section 15.7.7.6, “SHOW COLUMNS Statement” </a> , and <a class="xref" href="explain.html" title="15.8.2 EXPLAIN Statement"> Section 15.8.2, “EXPLAIN Statement” </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/group-replication-operations.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="group-replication-operations"> </a> 20.5 Group Replication Operations </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <span class="section"> <a href="group-replication-configuring-online-group.html"> 20.5.1 Configuring an Online Group </a> </span> </dt> <dt> <span class="section"> <a href="group-replication-restarting-group.html"> 20.5.2 Restarting a Group </a> </span> </dt> <dt> <span class="section"> <a href="group-replication-consistency-guarantees.html"> 20.5.3 Transaction Consistency Guarantees </a> </span> </dt> <dt> <span class="section"> <a href="group-replication-distributed-recovery.html"> 20.5.4 Distributed Recovery </a> </span> </dt> <dt> <span class="section"> <a href="group-replication-ipv6.html"> 20.5.5 Support For IPv6 And For Mixed IPv6 And IPv4 Groups </a> </span> </dt> <dt> <span class="section"> <a href="group-replication-enterprise-backup.html"> 20.5.6 Using MySQL Enterprise Backup with Group Replication </a> </span> </dt> </dl> </div> <a class="indexterm" name="idm46045133625440"> </a> <p> This section explains common operations for managing groups. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/telemetry-trace.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="telemetry-trace"> </a> 35.3 OpenTelemetry Trace </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <span class="section"> <a href="telemetry-trace-configuration.html"> 35.3.1 Configuring Trace Telemetry </a> </span> </dt> <dt> <span class="section"> <a href="telemetry-trace-format.html"> 35.3.2 Trace Format </a> </span> </dt> </dl> </div> <p> Tracing telemetry enables you to visualize the flow of any processing action as it is processed through your server. The data for each action, a span, includes possible error information and timing data. Traces are generated for <code class="literal"> COM_QUERY </code> commands executed, including non-query commands such as <code class="literal"> COM_PING </code> , or <code class="literal"> COM_STMT_CLOSE </code> . Query statement traces also have an associated SQL text attribute. </p> <p> Telemetry tracing is implemented in: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> MySQL Enterprise Edition Telemetry Component </p> </li> <li class="listitem"> <p> MySQL Enterprise Edition Client </p> </li> <li class="listitem"> <p> MySQL Connectors </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/optimizing-memory-tables.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="optimizing-memory-tables"> </a> 10.7 Optimizing for MEMORY Tables </h2> </div> </div> </div> <a class="indexterm" name="idm46045225633552"> </a> <p> Consider using <code class="literal"> MEMORY </code> tables for noncritical data that is accessed often, and is read-only or rarely updated. Benchmark your application against equivalent <code class="literal"> InnoDB </code> or <code class="literal"> MyISAM </code> tables under a realistic workload, to confirm that any additional performance is worth the risk of losing data, or the overhead of copying data from a disk-based table at application start. </p> <p> For best performance with <code class="literal"> MEMORY </code> tables, examine the kinds of queries against each table, and specify the type to use for each associated index, either a B-tree index or a hash index. On the <a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement"> <code class="literal"> CREATE INDEX </code> </a> statement, use the clause <code class="literal"> USING BTREE </code> or <code class="literal"> USING HASH </code> . B-tree indexes are fast for queries that do greater-than or less-than comparisons through operators such as <code class="literal"> > </code> or <code class="literal"> BETWEEN </code> . Hash indexes are only fast for queries that look up single values through the <code class="literal"> = </code> operator, or a restricted set of values through the <code class="literal"> IN </code> operator. For why <code class="literal"> USING BTREE </code> is often a better choice than the default <code class="literal"> USING HASH </code> , see <a class="xref" href="table-scan-avoidance.html" title="10.2.1.23 Avoiding Full Table Scans"> Section 10.2.1.23, “Avoiding Full Table Scans” </a> . For implementation details of the different types of <code class="literal"> MEMORY </code> indexes, see <a class="xref" href="index-btree-hash.html" title="10.3.9 Comparison of B-Tree and Hash Indexes"> Section 10.3.9, “Comparison of B-Tree and Hash Indexes” </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/replication-threads-monitor-main.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="replication-threads-monitor-main"> </a> 19.2.3.1 Monitoring Replication Main Threads </h4> </div> </div> </div> <p> The <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> statement provides information that tells you what is happening on the source and on the replica regarding replication. For information on source states, see <a class="xref" href="source-thread-states.html" title="10.14.4 Replication Source Thread States"> Section 10.14.4, “Replication Source Thread States” </a> . For replica states, see <a class="xref" href="replica-io-thread-states.html" title="10.14.5 Replication I/O (Receiver) Thread States"> Section 10.14.5, “Replication I/O (Receiver) Thread States” </a> , and <a class="xref" href="replica-sql-thread-states.html" title="10.14.6 Replication SQL Thread States"> Section 10.14.6, “Replication SQL Thread States” </a> . </p> <p> The following example illustrates how the three main replication threads, the binary log dump thread, replication I/O (receiver) thread, and replication SQL (applier) thread, show up in the output from <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> . </p> <p> On the source server, the output from <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> looks like this: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa53453033"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">PROCESSLIST</span>\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Id<span class="token punctuation">:</span> 2 User<span class="token punctuation">:</span> root Host<span class="token punctuation">:</span> localhost<span class="token punctuation">:</span>32931 db<span class="token punctuation">:</span> NULL Command<span class="token punctuation">:</span> Binlog Dump Time<span class="token punctuation">:</span> 94 State<span class="token punctuation">:</span> Has sent all binlog to slave; waiting for binlog to be updated Info<span class="token punctuation">:</span> NULL</span></code></pre> </div> <p> Here, thread 2 is a <code class="literal"> Binlog Dump </code> thread that services a connected replica. The <code class="literal"> State </code> information indicates that all outstanding updates have been sent to the replica and that the source is waiting for more updates to occur. If you see no <code class="literal"> Binlog Dump </code> threads on a source server, this means that replication is not running; that is, no replicas are currently connected. </p> <p> On a replica server, the output from <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> looks like this: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa82414362"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">PROCESSLIST</span>\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Id<span class="token punctuation">:</span> 10 User<span class="token punctuation">:</span> system user Host<span class="token punctuation">:</span> db<span class="token punctuation">:</span> NULL Command<span class="token punctuation">:</span> Connect Time<span class="token punctuation">:</span> 11 State<span class="token punctuation">:</span> Waiting for master to send event Info<span class="token punctuation">:</span> NULL <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 2. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Id<span class="token punctuation">:</span> 11 User<span class="token punctuation">:</span> system user Host<span class="token punctuation">:</span> db<span class="token punctuation">:</span> NULL Command<span class="token punctuation">:</span> Connect Time<span class="token punctuation">:</span> 11 State<span class="token punctuation">:</span> Has read all relay log; waiting for the slave I/O thread to update it Info<span class="token punctuation">:</span> NULL</span></code></pre> </div> <p> The <code class="literal"> State </code> information indicates that thread 10 is the replication I/O (receiver) thread that is communicating with the source server, and thread 11 is the replication SQL (applier) thread that is processing the updates stored in the relay logs. At the time that <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> was run, both threads were idle, waiting for further updates. </p> <p> The value in the <code class="literal"> Time </code> column can show how late the replica is compared to the source. See <a class="xref" href="faqs-replication.html" title="A.14 MySQL 8.4 FAQ: Replication"> Section A.14, “MySQL 8.4 FAQ: Replication” </a> . If sufficient time elapses on the source side without activity on the <code class="literal"> Binlog Dump </code> thread, the source determines that the replica is no longer connected. As for any other client connection, the timeouts for this depend on the values of <code class="option"> net_write_timeout </code> and <code class="option"> net_retry_count </code> ; for more information about these, see <a class="xref" href="server-system-variables.html" title="7.1.8 Server System Variables"> Section 7.1.8, “Server System Variables” </a> . </p> <p> The <a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement"> <code class="literal"> SHOW REPLICA STATUS </code> </a> statement provides additional information about replication processing on a replica server. See <a class="xref" href="replication-administration-status.html" title="19.1.7.1 Checking Replication Status"> Section 19.1.7.1, “Checking Replication Status” </a> . </p> <p> You can also retrieve information on the source's <code class="literal"> Binlog Dump </code> threads with the following: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa2700930"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>threads <span class="token keyword">WHERE</span> PROCESSLIST_COMMAND <span class="token operator">LIKE</span> <span class="token string">"Binlog Dump%"</span></code></pre> </div> <p> <code class="literal"> Binlog Dump% </code> is used to retrieve either <code class="literal"> Binlog Dump </code> or <code class="literal"> Binlog Dump GTID </code> , depending on which mode binlog dumping is in. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/partitioning-management-hash-key.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="partitioning-management-hash-key"> </a> 26.3.2 Management of HASH and KEY Partitions </h3> </div> </div> </div> <a class="indexterm" name="idm46045083734704"> </a> <a class="indexterm" name="idm46045083733216"> </a> <a class="indexterm" name="idm46045083731728"> </a> <a class="indexterm" name="idm46045083730240"> </a> <p> Tables which are partitioned by hash or by key are very similar to one another with regard to making changes in a partitioning setup, and both differ in a number of ways from tables which have been partitioned by range or list. For that reason, this section addresses the modification of tables partitioned by hash or by key only. For a discussion of adding and dropping of partitions of tables that are partitioned by range or list, see <a class="xref" href="partitioning-management-range-list.html" title="26.3.1 Management of RANGE and LIST Partitions"> Section 26.3.1, “Management of RANGE and LIST Partitions” </a> . </p> <p> You cannot drop partitions from tables that are partitioned by <code class="literal"> HASH </code> or <code class="literal"> KEY </code> in the same way that you can from tables that are partitioned by <code class="literal"> RANGE </code> or <code class="literal"> LIST </code> . However, you can merge <code class="literal"> HASH </code> or <code class="literal"> KEY </code> partitions using <code class="literal"> ALTER TABLE ... COALESCE PARTITION </code> . Suppose that a <code class="literal"> clients </code> table containing data about clients is divided into 12 partitions, created as shown here: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa79414721"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> clients <span class="token punctuation">(</span> id <span class="token datatype">INT</span><span class="token punctuation">,</span> fname <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">,</span> lname <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">signed</span> <span class="token datatype">DATE</span> <span class="token punctuation">)</span> <span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> <span class="token keyword">HASH</span><span class="token punctuation">(</span> <span class="token function">MONTH</span><span class="token punctuation">(</span><span class="token keyword">signed</span><span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token keyword">PARTITIONS</span> <span class="token number">12</span><span class="token punctuation">;</span></code></pre> </div> <p> To reduce the number of partitions from 12 to 8, execute the following <a class="link" href="alter-table-partition-operations.html" title="15.1.9.1 ALTER TABLE Partition Operations"> <code class="literal"> ALTER TABLE </code> </a> statement: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47927222"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> clients <span class="token keyword">COALESCE</span> <span class="token keyword">PARTITION</span> <span class="token number">4</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.02 sec)</span></code></pre> </div> <p> <code class="literal"> COALESCE </code> works equally well with tables that are partitioned by <code class="literal"> HASH </code> , <code class="literal"> KEY </code> , <code class="literal"> LINEAR HASH </code> , or <code class="literal"> LINEAR KEY </code> . Here is an example similar to the previous one, differing only in that the table is partitioned by <code class="literal"> LINEAR KEY </code> : </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81483131"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> clients_lk <span class="token punctuation">(</span> <span class="token prompt"> -></span> id <span class="token datatype">INT</span><span class="token punctuation">,</span> <span class="token prompt"> -></span> fname <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token prompt"> -></span> lname <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token keyword">signed</span> <span class="token datatype">DATE</span> <span class="token prompt"> -></span> <span class="token punctuation">)</span> <span class="token prompt"> -></span> <span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> <span class="token keyword">LINEAR</span> <span class="token keyword">KEY</span><span class="token punctuation">(</span><span class="token keyword">signed</span><span class="token punctuation">)</span> <span class="token prompt"> -></span> <span class="token keyword">PARTITIONS</span> <span class="token number">12</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.03 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> clients_lk <span class="token keyword">COALESCE</span> <span class="token keyword">PARTITION</span> <span class="token number">4</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.06 sec)</span> <span class="token output">Records: 0 Duplicates: 0 Warnings: 0</span></code></pre> </div> <p> The number following <code class="literal"> COALESCE PARTITION </code> is the number of partitions to merge into the remainder—in other words, it is the number of partitions to remove from the table. </p> <p> Attempting to remove more partitions than are in the table results in an error like this one: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa14288683"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> clients <span class="token keyword">COALESCE</span> <span class="token keyword">PARTITION</span> <span class="token number">18</span><span class="token punctuation">;</span> <span class="token output">ERROR 1478 (HY000)<span class="token punctuation">:</span> Cannot remove all partitions, use DROP TABLE instead</span></code></pre> </div> <p> To increase the number of partitions for the <code class="literal"> clients </code> table from 12 to 18, use <code class="literal"> ALTER TABLE ... ADD PARTITION </code> as shown here: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa48382134"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> clients <span class="token keyword">ADD</span> <span class="token keyword">PARTITION</span> <span class="token keyword">PARTITIONS</span> <span class="token number">6</span><span class="token punctuation">;</span></code></pre> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/group-replication-functions-for-communication-protocol.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="group-replication-functions-for-communication-protocol"> </a> 14.18.1.4 Functions to Inspect and Set the Group Replication Communication Protocol Version </h4> </div> </div> </div> <p> The following functions enable you to inspect and configure the Group Replication communication protocol version that is used by a replication group. </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <a class="xref" href="group-replication-message-compression.html" title="20.7.4 Message Compression"> Section 20.7.4, “Message Compression” </a> </p> </li> <li class="listitem"> <p> <a class="xref" href="group-replication-performance-message-fragmentation.html" title="20.7.5 Message Fragmentation"> Section 20.7.5, “Message Fragmentation” </a> </p> </li> <li class="listitem"> <p> <a class="xref" href="group-replication-single-consensus-leader.html" title="20.7.3 Single Consensus Leader"> Section 20.7.3, “Single Consensus Leader” </a> </p> </li> </ul> </div> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <a name="function_group-replication-get-communication-protocol"> </a> <a class="link" href="group-replication-functions-for-communication-protocol.html#function_group-replication-get-communication-protocol"> <code class="literal"> group_replication_get_communication_protocol() </code> </a> </p> <a class="indexterm" name="idm46045193806336"> </a> <a class="indexterm" name="idm46045193805232"> </a> <p> Inspect the Group Replication communication protocol version that is currently in use for a group. </p> <p> Syntax: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-clike"><div class="docs-select-all right" id="sa80884479"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike">STRING <span class="token function">group_replication_get_communication_protocol</span><span class="token punctuation">(</span><span class="token punctuation">)</span></code></pre> </div> <p> This function has no parameters. </p> <p> Return value: </p> <p> The oldest MySQL Server version that can join this group and use the group's communication protocol. Note that the <a class="link" href="group-replication-functions-for-communication-protocol.html#function_group-replication-get-communication-protocol"> <code class="literal"> group_replication_get_communication_protocol() </code> </a> function returns the minimum MySQL version that the group supports, which might differ from the version number that was passed to <a class="link" href="group-replication-functions-for-communication-protocol.html#function_group-replication-set-communication-protocol"> <code class="literal"> group_replication_set_communication_protocol() </code> </a> , and from the MySQL Server version that is installed on the member where you use the function. </p> <p> If the protocol cannot be inspected because this server instance does not belong to a replication group, an error is returned as a string. </p> <p> Example: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa13525648"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> group_replication_get_communication_protocol<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> group_replication_get_communication_protocol() <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 8.4.3 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> <p> For more information, see <a class="xref" href="group-replication-communication-protocol.html" title="20.5.1.4 Setting a Group's Communication Protocol Version"> Section 20.5.1.4, “Setting a Group's Communication Protocol Version” </a> . </p> </li> <li class="listitem"> <p> <a name="function_group-replication-set-communication-protocol"> </a> <a class="link" href="group-replication-functions-for-communication-protocol.html#function_group-replication-set-communication-protocol"> <code class="literal"> group_replication_set_communication_protocol() </code> </a> </p> <a class="indexterm" name="idm46045193790576"> </a> <a class="indexterm" name="idm46045193789472"> </a> <p> Downgrade the Group Replication communication protocol version of a group so that members at earlier releases can join, or upgrade the Group Replication communication protocol version of a group after upgrading MySQL Server on all members. The <a class="link" href="privileges-provided.html#priv_group-replication-admin"> <code class="literal"> GROUP_REPLICATION_ADMIN </code> </a> privilege is required to use this function, and all existing group members must be online when you issue the statement, with no loss of majority. </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> For MySQL InnoDB cluster, the communication protocol version is managed automatically whenever the cluster topology is changed using AdminAPI operations. You do not have to use these functions yourself for an InnoDB cluster. </p> </div> <p> Syntax: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-clike"><div class="docs-select-all right" id="sa88979436"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike">STRING <span class="token function">group_replication_set_communication_protocol</span><span class="token punctuation">(</span><em class="replaceable">version</em><span class="token punctuation">)</span></code></pre> </div> <p> Arguments: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> <em class="replaceable"> <code> version </code> </em> : For a downgrade, specify the MySQL Server version of the prospective group member that has the oldest installed server version. In this case, the command makes the group fall back to a communication protocol compatible with that server version if possible. The minimum server version that you can specify is MySQL 5.7.14. For an upgrade, specify the new MySQL Server version to which the existing group members have been upgraded. </p> </li> </ul> </div> <p> Return value: </p> <p> A string containing the result of the operation, for example whether it was successful or not. </p> <p> Example: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa38721772"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> group_replication_set_communication_protocol<span class="token punctuation">(</span><span class="token string">"5.7.25"</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre> </div> <p> For more information, see <a class="xref" href="group-replication-communication-protocol.html" title="20.5.1.4 Setting a Group's Communication Protocol Version"> Section 20.5.1.4, “Setting a Group's Communication Protocol Version” </a> . </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/window-functions-named-windows.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="window-functions-named-windows"> </a> 14.20.4 Named Windows </h3> </div> </div> </div> <a class="indexterm" name="idm46045191776896"> </a> <a class="indexterm" name="idm46045191775408"> </a> <p> Windows can be defined and given names by which to refer to them in <code class="literal"> OVER </code> clauses. To do this, use a <code class="literal"> WINDOW </code> clause. If present in a query, the <code class="literal"> WINDOW </code> clause falls between the positions of the <code class="literal"> HAVING </code> and <code class="literal"> ORDER BY </code> clauses, and has this syntax: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa32405680"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">WINDOW</span> <em class="replaceable">window_name</em> <span class="token keyword">AS</span> <span class="token punctuation">(</span><em class="replaceable">window_spec</em><span class="token punctuation">)</span> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">window_name</em> <span class="token keyword">AS</span> <span class="token punctuation">(</span><em class="replaceable">window_spec</em><span class="token punctuation">)</span><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre> </div> <p> For each window definition, <em class="replaceable"> <code> window_name </code> </em> is the window name, and <em class="replaceable"> <code> window_spec </code> </em> is the same type of window specification as given between the parentheses of an <code class="literal"> OVER </code> clause, as described in <a class="xref" href="window-functions-usage.html" title="14.20.2 Window Function Concepts and Syntax"> Section 14.20.2, “Window Function Concepts and Syntax” </a> : </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa18744139"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><em class="replaceable">window_spec</em>: <span class="token punctuation">[</span><em class="replaceable">window_name</em><span class="token punctuation">]</span> <span class="token punctuation">[</span><em class="replaceable">partition_clause</em><span class="token punctuation">]</span> <span class="token punctuation">[</span><em class="replaceable">order_clause</em><span class="token punctuation">]</span> <span class="token punctuation">[</span><em class="replaceable">frame_clause</em><span class="token punctuation">]</span></code></pre> </div> <p> A <code class="literal"> WINDOW </code> clause is useful for queries in which multiple <code class="literal"> OVER </code> clauses would otherwise define the same window. Instead, you can define the window once, give it a name, and refer to the name in the <code class="literal"> OVER </code> clauses. Consider this query, which defines the same window multiple times: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75536678"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> val<span class="token punctuation">,</span> <span class="token function">ROW_NUMBER</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">OVER</span> <span class="token punctuation">(</span><span class="token keyword">ORDER</span> <span class="token keyword">BY</span> val<span class="token punctuation">)</span> <span class="token keyword">AS</span> <span class="token string">'row_number'</span><span class="token punctuation">,</span> <span class="token function">RANK</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">OVER</span> <span class="token punctuation">(</span><span class="token keyword">ORDER</span> <span class="token keyword">BY</span> val<span class="token punctuation">)</span> <span class="token keyword">AS</span> <span class="token string">'rank'</span><span class="token punctuation">,</span> <span class="token function">DENSE_RANK</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">OVER</span> <span class="token punctuation">(</span><span class="token keyword">ORDER</span> <span class="token keyword">BY</span> val<span class="token punctuation">)</span> <span class="token keyword">AS</span> <span class="token string">'dense_rank'</span> <span class="token keyword">FROM</span> numbers<span class="token punctuation">;</span></code></pre> </div> <p> The query can be written more simply by using <code class="literal"> WINDOW </code> to define the window once and referring to the window by name in the <code class="literal"> OVER </code> clauses: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa66633455"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> val<span class="token punctuation">,</span> <span class="token function">ROW_NUMBER</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">OVER</span> w <span class="token keyword">AS</span> <span class="token string">'row_number'</span><span class="token punctuation">,</span> <span class="token function">RANK</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">OVER</span> w <span class="token keyword">AS</span> <span class="token string">'rank'</span><span class="token punctuation">,</span> <span class="token function">DENSE_RANK</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">OVER</span> w <span class="token keyword">AS</span> <span class="token string">'dense_rank'</span> <span class="token keyword">FROM</span> numbers <span class="token keyword">WINDOW</span> w <span class="token keyword">AS</span> <span class="token punctuation">(</span><span class="token keyword">ORDER</span> <span class="token keyword">BY</span> val<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre> </div> <p> A named window also makes it easier to experiment with the window definition to see the effect on query results. You need only modify the window definition in the <code class="literal"> WINDOW </code> clause, rather than multiple <code class="literal"> OVER </code> clause definitions. </p> <p> If an <code class="literal"> OVER </code> clause uses <code class="literal"> OVER ( <em class="replaceable"> <code> window_name </code> </em> ...) </code> rather than <code class="literal"> OVER <em class="replaceable"> <code> window_name </code> </em> </code> , the named window can be modified by the addition of other clauses. For example, this query defines a window that includes partitioning, and uses <code class="literal"> ORDER BY </code> in the <code class="literal"> OVER </code> clauses to modify the window in different ways: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa21721618"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token keyword">DISTINCT</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> <span class="token function">FIRST_VALUE</span><span class="token punctuation">(</span><span class="token datatype">year</span><span class="token punctuation">)</span> <span class="token keyword">OVER</span> <span class="token punctuation">(</span>w <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> <span class="token datatype">year</span> <span class="token keyword">ASC</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> <span class="token keyword">first</span><span class="token punctuation">,</span> <span class="token function">FIRST_VALUE</span><span class="token punctuation">(</span><span class="token datatype">year</span><span class="token punctuation">)</span> <span class="token keyword">OVER</span> <span class="token punctuation">(</span>w <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> <span class="token datatype">year</span> <span class="token keyword">DESC</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> <span class="token keyword">last</span> <span class="token keyword">FROM</span> sales <span class="token keyword">WINDOW</span> w <span class="token keyword">AS</span> <span class="token punctuation">(</span><span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> country<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre> </div> <p> An <code class="literal"> OVER </code> clause can only add properties to a named window, not modify them. If the named window definition includes a partitioning, ordering, or framing property, the <code class="literal"> OVER </code> clause that refers to the window name cannot also include the same kind of property or an error occurs: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> This construct is permitted because the window definition and the referring <code class="literal"> OVER </code> clause do not contain the same kind of properties: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa42050195"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">OVER</span> <span class="token punctuation">(</span>w <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> country<span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">WINDOW</span> w <span class="token keyword">AS</span> <span class="token punctuation">(</span><span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> country<span class="token punctuation">)</span></code></pre> </div> </li> <li class="listitem"> <p> This construct is not permitted because the <code class="literal"> OVER </code> clause specifies <code class="literal"> PARTITION BY </code> for a named window that already has <code class="literal"> PARTITION BY </code> : </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa7991103"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">OVER</span> <span class="token punctuation">(</span>w <span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> <span class="token datatype">year</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">WINDOW</span> w <span class="token keyword">AS</span> <span class="token punctuation">(</span><span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> country<span class="token punctuation">)</span></code></pre> </div> </li> </ul> </div> <p> The definition of a named window can itself begin with a <em class="replaceable"> <code> window_name </code> </em> . In such cases, forward and backward references are permitted, but not cycles: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> This is permitted; it contains forward and backward references but no cycles: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa61675262"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">WINDOW</span> w1 <span class="token keyword">AS</span> <span class="token punctuation">(</span>w2<span class="token punctuation">)</span><span class="token punctuation">,</span> w2 <span class="token keyword">AS</span> <span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> w3 <span class="token keyword">AS</span> <span class="token punctuation">(</span>w1<span class="token punctuation">)</span></code></pre> </div> </li> <li class="listitem"> <p> This is not permitted because it contains a cycle: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa94529933"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">WINDOW</span> w1 <span class="token keyword">AS</span> <span class="token punctuation">(</span>w2<span class="token punctuation">)</span><span class="token punctuation">,</span> w2 <span class="token keyword">AS</span> <span class="token punctuation">(</span>w3<span class="token punctuation">)</span><span class="token punctuation">,</span> w3 <span class="token keyword">AS</span> <span class="token punctuation">(</span>w1<span class="token punctuation">)</span></code></pre> </div> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/permission-optimization.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="permission-optimization"> </a> 10.2.6 Optimizing Database Privileges </h3> </div> </div> </div> <a class="indexterm" name="idm46045227611008"> </a> <a class="indexterm" name="idm46045227609552"> </a> <p> The more complex your privilege setup, the more overhead applies to all SQL statements. Simplifying the privileges established by <a class="link" href="grant.html" title="15.7.1.6 GRANT Statement"> <code class="literal"> GRANT </code> </a> statements enables MySQL to reduce permission-checking overhead when clients execute statements. For example, if you do not grant any table-level or column-level privileges, the server need not ever check the contents of the <code class="literal"> tables_priv </code> and <code class="literal"> columns_priv </code> tables. Similarly, if you place no resource limits on any accounts, the server does not have to perform resource counting. If you have a very high statement-processing load, consider using a simplified grant structure to reduce permission-checking overhead. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/show-procedure-status.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="show-procedure-status"> </a> 15.7.7.30 SHOW PROCEDURE STATUS Statement </h4> </div> </div> </div> <a class="indexterm" name="idm46045169953648"> </a> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34616638"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SHOW</span> <span class="token keyword">PROCEDURE</span> <span class="token keyword">STATUS</span> <span class="token punctuation">[</span><span class="token operator">LIKE</span> <span class="token string">'<em class="replaceable">pattern</em>'</span> <span class="token operator">\|</span> <span class="token keyword">WHERE</span> <em class="replaceable">expr</em><span class="token punctuation">]</span></code></pre> </div> <p> This statement is a MySQL extension. It returns characteristics of a stored procedure, such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, <a class="link" href="show-function-status.html" title="15.7.7.21 SHOW FUNCTION STATUS Statement"> <code class="literal"> SHOW FUNCTION STATUS </code> </a> , displays information about stored functions (see <a class="xref" href="show-function-status.html" title="15.7.7.21 SHOW FUNCTION STATUS Statement"> Section 15.7.7.21, “SHOW FUNCTION STATUS Statement” </a> ). </p> <p> To use either statement, you must be the user named as the routine <code class="literal"> DEFINER </code> , have the <a class="link" href="privileges-provided.html#priv_show-routine"> <code class="literal"> SHOW_ROUTINE </code> </a> privilege, have the <a class="link" href="privileges-provided.html#priv_select"> <code class="literal"> SELECT </code> </a> privilege at the global level, or have the <a class="link" href="privileges-provided.html#priv_create-routine"> <code class="literal"> CREATE ROUTINE </code> </a> , <a class="link" href="privileges-provided.html#priv_alter-routine"> <code class="literal"> ALTER ROUTINE </code> </a> , or <a class="link" href="privileges-provided.html#priv_execute"> <code class="literal"> EXECUTE </code> </a> privilege granted at a scope that includes the routine. </p> <p> The <a class="link" href="string-comparison-functions.html#operator_like"> <code class="literal"> LIKE </code> </a> clause, if present, indicates which procedure or function names to match. The <code class="literal"> WHERE </code> clause can be given to select rows using more general conditions, as discussed in <a class="xref" href="extended-show.html" title="28.8 Extensions to SHOW Statements"> Section 28.8, “Extensions to SHOW Statements” </a> . </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16724578"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">PROCEDURE</span> <span class="token keyword">STATUS</span> <span class="token operator">LIKE</span> <span class="token string">'sp1'</span>\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Db<span class="token punctuation">:</span> test Name<span class="token punctuation">:</span> sp1 Type<span class="token punctuation">:</span> PROCEDURE Definer<span class="token punctuation">:</span> testuser@localhost Modified<span class="token punctuation">:</span> 2018-08-08 13<span class="token punctuation">:</span>54<span class="token punctuation">:</span>11 Created<span class="token punctuation">:</span> 2018-08-08 13<span class="token punctuation">:</span>54<span class="token punctuation">:</span>11 Security_type<span class="token punctuation">:</span> DEFINER Comment<span class="token punctuation">:</span> character_set_client<span class="token punctuation">:</span> utf8mb4 collation_connection<span class="token punctuation">:</span> utf8mb4_0900_ai_ci Database Collation<span class="token punctuation">:</span> utf8mb4_0900_ai_ci </span> <span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">FUNCTION</span> <span class="token keyword">STATUS</span> <span class="token operator">LIKE</span> <span class="token string">'hello'</span>\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Db<span class="token punctuation">:</span> test Name<span class="token punctuation">:</span> hello Type<span class="token punctuation">:</span> FUNCTION Definer<span class="token punctuation">:</span> testuser@localhost Modified<span class="token punctuation">:</span> 2020-03-10 11<span class="token punctuation">:</span>10<span class="token punctuation">:</span>03 Created<span class="token punctuation">:</span> 2020-03-10 11<span class="token punctuation">:</span>10<span class="token punctuation">:</span>03 Security_type<span class="token punctuation">:</span> DEFINER Comment<span class="token punctuation">:</span> character_set_client<span class="token punctuation">:</span> utf8mb4 collation_connection<span class="token punctuation">:</span> utf8mb4_0900_ai_ci Database Collation<span class="token punctuation">:</span> utf8mb4_0900_ai_ci</span></code></pre> </div> <p> <code class="literal"> character_set_client </code> is the session value of the <a class="link" href="server-system-variables.html#sysvar_character_set_client"> <code class="literal"> character_set_client </code> </a> system variable when the routine was created. <code class="literal"> collation_connection </code> is the session value of the <a class="link" href="server-system-variables.html#sysvar_collation_connection"> <code class="literal"> collation_connection </code> </a> system variable when the routine was created. <code class="literal"> Database Collation </code> is the collation of the database with which the routine is associated. </p> <p> Stored routine information is also available from the <code class="literal"> INFORMATION_SCHEMA </code> <a class="link" href="information-schema-parameters-table.html" title="28.3.20 The INFORMATION_SCHEMA PARAMETERS Table"> <code class="literal"> PARAMETERS </code> </a> and <a class="link" href="information-schema-routines-table.html" title="28.3.30 The INFORMATION_SCHEMA ROUTINES Table"> <code class="literal"> ROUTINES </code> </a> tables. See <a class="xref" href="information-schema-parameters-table.html" title="28.3.20 The INFORMATION_SCHEMA PARAMETERS Table"> Section 28.3.20, “The INFORMATION_SCHEMA PARAMETERS Table” </a> , and <a class="xref" href="information-schema-routines-table.html" title="28.3.30 The INFORMATION_SCHEMA ROUTINES Table"> Section 28.3.30, “The INFORMATION_SCHEMA ROUTINES Table” </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-statement-summary-tables.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="performance-schema-statement-summary-tables"> </a> 29.12.20.3 Statement Summary Tables </h4> </div> </div> </div> <a class="indexterm" name="idm46045068967088"> </a> <a class="indexterm" name="idm46045068965552"> </a> <a class="indexterm" name="idm46045068964016"> </a> <a class="indexterm" name="idm46045068962560"> </a> <a class="indexterm" name="idm46045068961040"> </a> <a class="indexterm" name="idm46045068959520"> </a> <a class="indexterm" name="idm46045068958000"> </a> <a class="indexterm" name="idm46045068956480"> </a> <a class="indexterm" name="idm46045068954960"> </a> <a class="indexterm" name="idm46045068953440"> </a> <a class="indexterm" name="idm46045068951920"> </a> <a class="indexterm" name="idm46045068950400"> </a> <a class="indexterm" name="idm46045068948880"> </a> <a class="indexterm" name="idm46045068947360"> </a> <a class="indexterm" name="idm46045068945840"> </a> <a class="indexterm" name="idm46045068944336"> </a> <p> The Performance Schema maintains tables for collecting current and recent statement events, and aggregates that information in summary tables. <a class="xref" href="performance-schema-statement-tables.html" title="29.12.6 Performance Schema Statement Event Tables"> Section 29.12.6, “Performance Schema Statement Event Tables” </a> describes the events on which statement summaries are based. See that discussion for information about the content of statement events, the current and historical statement event tables, and how to control statement event collection, which is partially disabled by default. </p> <p> Example statement event summary information: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa525453"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>events_statements_summary_global_by_event_name\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation">*</span> EVENT_NAME<span class="token punctuation">:</span> statement/sql/select COUNT_STAR<span class="token punctuation">:</span> 54 SUM_TIMER_WAIT<span class="token punctuation">:</span> 38860400000 MIN_TIMER_WAIT<span class="token punctuation">:</span> 52400000 AVG_TIMER_WAIT<span class="token punctuation">:</span> 719600000 MAX_TIMER_WAIT<span class="token punctuation">:</span> 12631800000 SUM_LOCK_TIME<span class="token punctuation">:</span> 88000000 SUM_ERRORS<span class="token punctuation">:</span> 0 SUM_WARNINGS<span class="token punctuation">:</span> 0 SUM_ROWS_AFFECTED<span class="token punctuation">:</span> 0 SUM_ROWS_SENT<span class="token punctuation">:</span> 60 SUM_ROWS_EXAMINED<span class="token punctuation">:</span> 120 SUM_CREATED_TMP_DISK_TABLES<span class="token punctuation">:</span> 0 SUM_CREATED_TMP_TABLES<span class="token punctuation">:</span> 21 SUM_SELECT_FULL_JOIN<span class="token punctuation">:</span> 16 SUM_SELECT_FULL_RANGE_JOIN<span class="token punctuation">:</span> 0 SUM_SELECT_RANGE<span class="token punctuation">:</span> 0 SUM_SELECT_RANGE_CHECK<span class="token punctuation">:</span> 0 SUM_SELECT_SCAN<span class="token punctuation">:</span> 41 SUM_SORT_MERGE_PASSES<span class="token punctuation">:</span> 0 SUM_SORT_RANGE<span class="token punctuation">:</span> 0 SUM_SORT_ROWS<span class="token punctuation">:</span> 0 SUM_SORT_SCAN<span class="token punctuation">:</span> 0 SUM_NO_INDEX_USED<span class="token punctuation">:</span> 22 SUM_NO_GOOD_INDEX_USED<span class="token punctuation">:</span> 0 SUM_CPU_TIME<span class="token punctuation">:</span> 0 MAX_CONTROLLED_MEMORY<span class="token punctuation">:</span> 2028360 MAX_TOTAL_MEMORY<span class="token punctuation">:</span> 2853429 COUNT_SECONDARY<span class="token punctuation">:</span> 0 ...</span></code></pre> </div> <p> Each statement summary table has one or more grouping columns to indicate how the table aggregates events. Event names refer to names of event instruments in the <a class="link" href="performance-schema-setup-instruments-table.html" title="29.12.2.3 The setup_instruments Table"> <code class="literal"> setup_instruments </code> </a> table: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_account_by_event_name </code> </a> has <code class="literal"> EVENT_NAME </code> , <code class="literal"> USER </code> , and <code class="literal"> HOST </code> columns. Each row summarizes events for a given account (user and host combination) and event name. </p> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> has <code class="literal"> SCHEMA_NAME </code> and <code class="literal"> DIGEST </code> columns. Each row summarizes events per schema and digest value. (The <code class="literal"> DIGEST_TEXT </code> column contains the corresponding normalized statement digest text, but is neither a grouping nor a summary column. The <code class="literal"> QUERY_SAMPLE_TEXT </code> , <code class="literal"> QUERY_SAMPLE_SEEN </code> , and <code class="literal"> QUERY_SAMPLE_TIMER_WAIT </code> columns also are neither grouping nor summary columns; they support statement sampling.) </p> <p> The maximum number of rows in the table is autosized at server startup. To set this maximum explicitly, set the <a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_digests_size"> <code class="literal"> performance_schema_digests_size </code> </a> system variable at server startup. </p> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_host_by_event_name </code> </a> has <code class="literal"> EVENT_NAME </code> and <code class="literal"> HOST </code> columns. Each row summarizes events for a given host and event name. </p> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_program </code> </a> has <code class="literal"> OBJECT_TYPE </code> , <code class="literal"> OBJECT_SCHEMA </code> , and <code class="literal"> OBJECT_NAME </code> columns. Each row summarizes events for a given stored program (stored procedure or function, trigger, or event). </p> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_thread_by_event_name </code> </a> has <code class="literal"> THREAD_ID </code> and <code class="literal"> EVENT_NAME </code> columns. Each row summarizes events for a given thread and event name. </p> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_user_by_event_name </code> </a> has <code class="literal"> EVENT_NAME </code> and <code class="literal"> USER </code> columns. Each row summarizes events for a given user and event name. </p> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_global_by_event_name </code> </a> has an <code class="literal"> EVENT_NAME </code> column. Each row summarizes events for a given event name. </p> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-prepared-statements-instances-table.html" title="29.12.6.4 The prepared_statements_instances Table"> <code class="literal"> prepared_statements_instances </code> </a> has an <code class="literal"> OBJECT_INSTANCE_BEGIN </code> column. Each row summarizes events for a given prepared statement. </p> </li> </ul> </div> <p> Each statement summary table has these summary columns containing aggregated values (with exceptions as noted): </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> COUNT_STAR </code> , <code class="literal"> SUM_TIMER_WAIT </code> , <code class="literal"> MIN_TIMER_WAIT </code> , <code class="literal"> AVG_TIMER_WAIT </code> , <code class="literal"> MAX_TIMER_WAIT </code> </p> <p> These columns are analogous to the columns of the same names in the wait event summary tables (see <a class="xref" href="performance-schema-wait-summary-tables.html" title="29.12.20.1 Wait Event Summary Tables"> Section 29.12.20.1, “Wait Event Summary Tables” </a> ), except that the statement summary tables aggregate events from <a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table"> <code class="literal"> events_statements_current </code> </a> rather than <a class="link" href="performance-schema-events-waits-current-table.html" title="29.12.4.1 The events_waits_current Table"> <code class="literal"> events_waits_current </code> </a> . </p> <p> The <a class="link" href="performance-schema-prepared-statements-instances-table.html" title="29.12.6.4 The prepared_statements_instances Table"> <code class="literal"> prepared_statements_instances </code> </a> table does not have these columns. </p> </li> <li class="listitem"> <p> <code class="literal"> SUM_ <em class="replaceable"> <code> xxx </code> </em> </code> </p> <p> The aggregate of the corresponding <em class="replaceable"> <code> xxx </code> </em> column in the <a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table"> <code class="literal"> events_statements_current </code> </a> table. For example, the <code class="literal"> SUM_LOCK_TIME </code> and <code class="literal"> SUM_ERRORS </code> columns in statement summary tables are the aggregates of the <code class="literal"> LOCK_TIME </code> and <code class="literal"> ERRORS </code> columns in <a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table"> <code class="literal"> events_statements_current </code> </a> table. </p> </li> <li class="listitem"> <p> <code class="literal"> MAX_CONTROLLED_MEMORY </code> </p> <p> Reports the maximum amount of controlled memory used by a statement during execution. </p> </li> <li class="listitem"> <p> <code class="literal"> MAX_TOTAL_MEMORY </code> </p> <p> Reports the maximum amount of memory used by a statement during execution. </p> </li> <li class="listitem"> <p> <code class="literal"> COUNT_SECONDARY </code> </p> <p> The number of times a query was processed on the <code class="literal"> SECONDARY </code> engine. For use with HeatWave Service and HeatWave, where the <code class="literal"> PRIMARY </code> engine is <code class="literal"> InnoDB </code> and the <code class="literal"> SECONDARY </code> engine is HeatWave ( <code class="literal"> RAPID </code> ). For MySQL Community Edition Server, MySQL Enterprise Edition Server (on-premise), and HeatWave Service without HeatWave, queries are always processed on the <code class="literal"> PRIMARY </code> engine, which means the value is always 0 on these MySQL Servers. </p> </li> </ul> </div> <p> The <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> table has these additional summary columns: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> FIRST_SEEN </code> , <code class="literal"> LAST_SEEN </code> </p> <p> Timestamps indicating when statements with the given digest value were first seen and most recently seen. </p> </li> <li class="listitem"> <p> <code class="literal"> QUANTILE_95 </code> : The 95th percentile of the statement latency, in picoseconds. This percentile is a high estimate, computed from the histogram data collected. In other words, for a given digest, 95% of the statements measured have a latency lower than <code class="literal"> QUANTILE_95 </code> . </p> <p> For access to the histogram data, use the tables described in <a class="xref" href="performance-schema-statement-histogram-summary-tables.html" title="29.12.20.4 Statement Histogram Summary Tables"> Section 29.12.20.4, “Statement Histogram Summary Tables” </a> . </p> </li> <li class="listitem"> <p> <code class="literal"> QUANTILE_99 </code> : Similar to <code class="literal"> QUANTILE_95 </code> , but for the 99th percentile. </p> </li> <li class="listitem"> <p> <code class="literal"> QUANTILE_999 </code> : Similar to <code class="literal"> QUANTILE_95 </code> , but for the 99.9th percentile. </p> </li> </ul> </div> <p> The <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> table contains the following columns. These are neither grouping nor summary columns; they support statement sampling: </p> <a class="indexterm" name="idm46045068856048"> </a> <a class="indexterm" name="idm46045068854976"> </a> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> QUERY_SAMPLE_TEXT </code> </p> <p> A sample SQL statement that produces the digest value in the row. This column enables applications to access, for a given digest value, a statement actually seen by the server that produces that digest. One use for this might be to run <a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement"> <code class="literal"> EXPLAIN </code> </a> on the statement to examine the execution plan for a representative statement associated with a frequently occurring digest. </p> <p> When the <code class="literal"> QUERY_SAMPLE_TEXT </code> column is assigned a value, the <code class="literal"> QUERY_SAMPLE_SEEN </code> and <code class="literal"> QUERY_SAMPLE_TIMER_WAIT </code> columns are assigned values as well. </p> <p> The maximum space available for statement display is 1024 bytes by default. To change this value, set the <a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_sql_text_length"> <code class="literal"> performance_schema_max_sql_text_length </code> </a> system variable at server startup. (Changing this value affects columns in other Performance Schema tables as well. See <a class="xref" href="performance-schema-statement-digests.html" title="29.10 Performance Schema Statement Digests and Sampling"> Section 29.10, “Performance Schema Statement Digests and Sampling” </a> .) </p> <p> For information about statement sampling, see <a class="xref" href="performance-schema-statement-digests.html" title="29.10 Performance Schema Statement Digests and Sampling"> Section 29.10, “Performance Schema Statement Digests and Sampling” </a> . </p> </li> <li class="listitem"> <p> <code class="literal"> QUERY_SAMPLE_SEEN </code> </p> <p> A timestamp indicating when the statement in the <code class="literal"> QUERY_SAMPLE_TEXT </code> column was seen. </p> </li> <li class="listitem"> <p> <code class="literal"> QUERY_SAMPLE_TIMER_WAIT </code> </p> <p> The wait time for the sample statement in the <code class="literal"> QUERY_SAMPLE_TEXT </code> column. </p> </li> </ul> </div> <p> The <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_program </code> </a> table has these additional summary columns: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> COUNT_STATEMENTS </code> , <code class="literal"> SUM_STATEMENTS_WAIT </code> , <code class="literal"> MIN_STATEMENTS_WAIT </code> , <code class="literal"> AVG_STATEMENTS_WAIT </code> , <code class="literal"> MAX_STATEMENTS_WAIT </code> </p> <p> Statistics about nested statements invoked during stored program execution. </p> </li> </ul> </div> <p> The <a class="link" href="performance-schema-prepared-statements-instances-table.html" title="29.12.6.4 The prepared_statements_instances Table"> <code class="literal"> prepared_statements_instances </code> </a> table has these additional summary columns: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> COUNT_EXECUTE </code> , <code class="literal"> SUM_TIMER_EXECUTE </code> , <code class="literal"> MIN_TIMER_EXECUTE </code> , <code class="literal"> AVG_TIMER_EXECUTE </code> , <code class="literal"> MAX_TIMER_EXECUTE </code> </p> <p> Aggregated statistics for executions of the prepared statement. </p> </li> </ul> </div> <p> The statement summary tables have these indexes: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables"> <code class="literal"> events_transactions_summary_by_account_by_event_name </code> </a> : </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> Primary key on ( <code class="literal"> USER </code> , <code class="literal"> HOST </code> , <code class="literal"> EVENT_NAME </code> ) </p> </li> </ul> </div> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> : </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> Primary key on ( <code class="literal"> SCHEMA_NAME </code> , <code class="literal"> DIGEST </code> ) </p> </li> </ul> </div> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables"> <code class="literal"> events_transactions_summary_by_host_by_event_name </code> </a> : </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> Primary key on ( <code class="literal"> HOST </code> , <code class="literal"> EVENT_NAME </code> ) </p> </li> </ul> </div> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_program </code> </a> : </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> Primary key on ( <code class="literal"> OBJECT_TYPE </code> , <code class="literal"> OBJECT_SCHEMA </code> , <code class="literal"> OBJECT_NAME </code> ) </p> </li> </ul> </div> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_thread_by_event_name </code> </a> : </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> Primary key on ( <code class="literal"> THREAD_ID </code> , <code class="literal"> EVENT_NAME </code> ) </p> </li> </ul> </div> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables"> <code class="literal"> events_transactions_summary_by_user_by_event_name </code> </a> : </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> Primary key on ( <code class="literal"> USER </code> , <code class="literal"> EVENT_NAME </code> ) </p> </li> </ul> </div> </li> <li class="listitem"> <p> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_global_by_event_name </code> </a> : </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> Primary key on ( <code class="literal"> EVENT_NAME </code> ) </p> </li> </ul> </div> </li> </ul> </div> <p> <a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement"> <code class="literal"> TRUNCATE TABLE </code> </a> is permitted for statement summary tables. It has these effects: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> For <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> , it removes the rows. </p> </li> <li class="listitem"> <p> For other summary tables not aggregated by account, host, or user, truncation resets the summary columns to zero rather than removing rows. </p> </li> <li class="listitem"> <p> For other summary tables aggregated by account, host, or user, truncation removes rows for accounts, hosts, or users with no connections, and resets the summary columns to zero for the remaining rows. </p> </li> </ul> </div> <p> In addition, each statement summary table that is aggregated by account, host, user, or thread is implicitly truncated by truncation of the connection table on which it depends, or truncation of <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_global_by_event_name </code> </a> . For details, see <a class="xref" href="performance-schema-connection-tables.html" title="29.12.8 Performance Schema Connection Tables"> Section 29.12.8, “Performance Schema Connection Tables” </a> . </p> <p> In addition, truncating <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> implicitly truncates <a class="link" href="performance-schema-statement-histogram-summary-tables.html" title="29.12.20.4 Statement Histogram Summary Tables"> <code class="literal"> events_statements_histogram_by_digest </code> </a> , and truncating <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_global_by_event_name </code> </a> implicitly truncates <a class="link" href="performance-schema-statement-histogram-summary-tables.html" title="29.12.20.4 Statement Histogram Summary Tables"> <code class="literal"> events_statements_histogram_global </code> </a> . </p> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="statement-summary-tables-aggregation"> </a> Statement Digest Aggregation Rules </h5> </div> </div> </div> <p> If the <code class="literal"> statements_digest </code> consumer is enabled, aggregation into <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> occurs as follows when a statement completes. Aggregation is based on the <code class="literal"> DIGEST </code> value computed for the statement. </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> If a <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> row already exists with the digest value for the statement that just completed, statistics for the statement are aggregated to that row. The <code class="literal"> LAST_SEEN </code> column is updated to the current time. </p> </li> <li class="listitem"> <p> If no row has the digest value for the statement that just completed, and the table is not full, a new row is created for the statement. The <code class="literal"> FIRST_SEEN </code> and <code class="literal"> LAST_SEEN </code> columns are initialized with the current time. </p> </li> <li class="listitem"> <p> If no row has the statement digest value for the statement that just completed, and the table is full, the statistics for the statement that just completed are added to a special <span class="quote"> “ <span class="quote"> catch-all </span> ” </span> row with <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> , which is created if necessary. If the row is created, the <code class="literal"> FIRST_SEEN </code> and <code class="literal"> LAST_SEEN </code> columns are initialized with the current time. Otherwise, the <code class="literal"> LAST_SEEN </code> column is updated with the current time. </p> </li> </ul> </div> <p> The row with <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> is maintained because Performance Schema tables have a maximum size due to memory constraints. The <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> row permits digests that do not match other rows to be counted even if the summary table is full, using a common <span class="quote"> “ <span class="quote"> other </span> ” </span> bucket. This row helps you estimate whether the digest summary is representative: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> A <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> row that has a <code class="literal"> COUNT_STAR </code> value that represents 5% of all digests shows that the digest summary table is very representative; the other rows cover 95% of the statements seen. </p> </li> <li class="listitem"> <p> A <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> row that has a <code class="literal"> COUNT_STAR </code> value that represents 50% of all digests shows that the digest summary table is not very representative; the other rows cover only half the statements seen. Most likely the DBA should increase the maximum table size so that more of the rows counted in the <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> row would be counted using more specific rows instead. By default, the table is autosized, but if this size is too small, set the <a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_digests_size"> <code class="literal"> performance_schema_digests_size </code> </a> system variable to a larger value at server startup. </p> </li> </ul> </div> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="statement-summary-tables-stored-programs"> </a> Stored Program Instrumentation Behavior </h5> </div> </div> </div> <p> For stored program types for which instrumentation is enabled in the <a class="link" href="performance-schema-setup-objects-table.html" title="29.12.2.4 The setup_objects Table"> <code class="literal"> setup_objects </code> </a> table, <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_program </code> </a> maintains statistics for stored programs as follows: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> A row is added for an object when it is first used in the server. </p> </li> <li class="listitem"> <p> The row for an object is removed when the object is dropped. </p> </li> <li class="listitem"> <p> Statistics are aggregated in the row for an object as it executes. </p> </li> </ul> </div> <p> See also <a class="xref" href="performance-schema-pre-filtering.html" title="29.4.3 Event Pre-Filtering"> Section 29.4.3, “Event Pre-Filtering” </a> . </p> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-backup-troubleshooting.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysql-cluster-backup-troubleshooting"> </a> 25.6.8.4 NDB Cluster Backup Troubleshooting </h4> </div> </div> </div> <a class="indexterm" name="idm46045091920160"> </a> <a class="indexterm" name="idm46045091918672"> </a> <a class="indexterm" name="idm46045091917184"> </a> <p> If an error code is returned when issuing a backup request, the most likely cause is insufficient memory or disk space. You should check that there is enough memory allocated for the backup. </p> <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Important </div> <p> If you have set <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-backupdatabuffersize"> <code class="literal"> BackupDataBufferSize </code> </a> and <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-backuplogbuffersize"> <code class="literal"> BackupLogBufferSize </code> </a> and their sum is greater than 4MB, then you must also set <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-backupmemory"> <code class="literal"> BackupMemory </code> </a> as well. </p> </div> <p> You should also make sure that there is sufficient space on the hard drive partition of the backup target. </p> <p> <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> does not support repeatable reads, which can cause problems with the restoration process. Although the backup process is <span class="quote"> “ <span class="quote"> hot </span> ” </span> , restoring an NDB Cluster from backup is not a 100% <span class="quote"> “ <span class="quote"> hot </span> ” </span> process. This is due to the fact that, for the duration of the restore process, running transactions get nonrepeatable reads from the restored data. This means that the state of the data is inconsistent while the restore is in progress. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/fetching-spatial-data.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="fetching-spatial-data"> </a> 13.4.8 Fetching Spatial Data </h3> </div> </div> </div> <p> Geometry values stored in a table can be fetched in internal format. You can also convert them to WKT or WKB format. </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> Fetching spatial data in internal format: </p> <p> Fetching geometry values using internal format can be useful in table-to-table transfers: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa34993663"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> geom2 <span class="token punctuation">(</span>g <span class="token keyword">GEOMETRY</span><span class="token punctuation">)</span> <span class="token keyword">SELECT</span> g <span class="token keyword">FROM</span> geom<span class="token punctuation">;</span></code></pre> </div> </li> <li class="listitem"> <p> Fetching spatial data in WKT format: </p> <p> The <a class="link" href="gis-format-conversion-functions.html#function_st-astext"> <code class="literal"> ST_AsText() </code> </a> function converts a geometry from internal format to a WKT string. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa49038250"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">ST_AsText</span><span class="token punctuation">(</span>g<span class="token punctuation">)</span> <span class="token keyword">FROM</span> geom<span class="token punctuation">;</span></code></pre> </div> </li> <li class="listitem"> <p> Fetching spatial data in WKB format: </p> <p> The <a class="link" href="gis-format-conversion-functions.html#function_st-asbinary"> <code class="literal"> ST_AsBinary() </code> </a> function converts a geometry from internal format to a <a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types"> <code class="literal"> BLOB </code> </a> containing the WKB value. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa39383153"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">ST_AsBinary</span><span class="token punctuation">(</span>g<span class="token punctuation">)</span> <span class="token keyword">FROM</span> geom<span class="token punctuation">;</span></code></pre> </div> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replication-issues.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="mysql-cluster-replication-issues"> </a> 25.7.3 Known Issues in NDB Cluster Replication </h3> </div> </div> </div> <a class="indexterm" name="idm46045086732400"> </a> <p> This section discusses known problems or issues when using replication with NDB Cluster. </p> <p> <b> Loss of connection between source and replica. </b> <a class="indexterm" name="idm46045086729472"> </a> A loss of connection can occur either between the source cluster SQL node and the replica cluster SQL node, or between the source SQL node and the data nodes of the source cluster. In the latter case, this can occur not only as a result of loss of physical connection (for example, a broken network cable), but due to the overflow of data node event buffers; if the SQL node is too slow to respond, it may be dropped by the cluster (this is controllable to some degree by adjusting the <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-maxbufferedepochs"> <code class="literal"> MaxBufferedEpochs </code> </a> and <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-timebetweenepochs"> <code class="literal"> TimeBetweenEpochs </code> </a> configuration parameters). If this occurs, <span class="emphasis"> <em> it is entirely possible for new data to be inserted into the source cluster without being recorded in the source SQL node's binary log </em> </span> . For this reason, to guarantee high availability, it is extremely important to maintain a backup replication channel, to monitor the primary channel, and to fail over to the secondary replication channel when necessary to keep the replica cluster synchronized with the source. NDB Cluster is not designed to perform such monitoring on its own; for this, an external application is required. </p> <p> <a class="indexterm" name="idm46045086723264"> </a> <a class="indexterm" name="idm46045086721776"> </a> The source SQL node issues a <span class="quote"> “ <span class="quote"> gap </span> ” </span> event when connecting or reconnecting to the source cluster. (A gap event is a type of <span class="quote"> “ <span class="quote"> incident event, </span> ” </span> which indicates an incident that occurs that affects the contents of the database but that cannot easily be represented as a set of changes. Examples of incidents are server failures, database resynchronization, some software updates, and some hardware changes.) When the replica encounters a gap in the replication log, it stops with an error message. This message is available in the output of <a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement"> <code class="literal"> SHOW REPLICA STATUS </code> </a> , and indicates that the SQL thread has stopped due to an incident registered in the replication stream, and that manual intervention is required. See <a class="xref" href="mysql-cluster-replication-failover.html" title="25.7.8 Implementing Failover with NDB Cluster Replication"> Section 25.7.8, “Implementing Failover with NDB Cluster Replication” </a> , for more information about what to do in such circumstances. </p> <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Important </div> <p> Because NDB Cluster is not designed on its own to monitor replication status or provide failover, if high availability is a requirement for the replica server or cluster, then you must set up multiple replication lines, monitor the source <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server"> <span class="command"> <strong> mysqld </strong> </span> </a> on the primary replication line, and be prepared fail over to a secondary line if and as necessary. This must be done manually, or possibly by means of a third-party application. For information about implementing this type of setup, see <a class="xref" href="mysql-cluster-replication-two-channels.html" title="25.7.7 Using Two Replication Channels for NDB Cluster Replication"> Section 25.7.7, “Using Two Replication Channels for NDB Cluster Replication” </a> , and <a class="xref" href="mysql-cluster-replication-failover.html" title="25.7.8 Implementing Failover with NDB Cluster Replication"> Section 25.7.8, “Implementing Failover with NDB Cluster Replication” </a> . </p> <p> If you are replicating from a standalone MySQL server to an NDB Cluster, one channel is usually sufficient. </p> </div> <p> <b> Circular replication. </b> <a class="indexterm" name="idm46045086710848"> </a> <a class="indexterm" name="idm46045086709360"> </a> <a class="indexterm" name="idm46045086707872"> </a> NDB Cluster Replication supports circular replication, as shown in the next example. The replication setup involves three NDB Clusters numbered 1, 2, and 3, in which Cluster 1 acts as the replication source for Cluster 2, Cluster 2 acts as the source for Cluster 3, and Cluster 3 acts as the source for Cluster 1, thus completing the circle. Each NDB Cluster has two SQL nodes, with SQL nodes A and B belonging to Cluster 1, SQL nodes C and D belonging to Cluster 2, and SQL nodes E and F belonging to Cluster 3. </p> <p> Circular replication using these clusters is supported as long as the following conditions are met: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> The SQL nodes on all source and replica clusters are the same. </p> </li> <li class="listitem"> <p> All SQL nodes acting as sources and replicas are started with the system variable <a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates"> <code class="literal"> log_replica_updates </code> </a> enabled. </p> </li> </ul> </div> <p> This type of circular replication setup is shown in the following diagram: </p> <div class="figure"> <a name="fig-mysql-cluster-circular-all-sources-replicas"> </a> <p class="title"> <b> Figure 25.11 NDB Cluster Circular Replication With All Sources As Replicas </b> </p> <div class="figure-contents"> <div class="mediaobject"> <img alt="Some content is described in the surrounding text. The diagram shows three clusters, each with two nodes. Arrows connecting SQL nodes in different clusters illustrate that all sources are also replicas." src="images/cluster-circular-replication-1.png" style="width: 100%; max-width: 557px;"/> </div> </div> </div> <br class="figure-break"/> <p> In this scenario, SQL node A in Cluster 1 replicates to SQL node C in Cluster 2; SQL node C replicates to SQL node E in Cluster 3; SQL node E replicates to SQL node A. In other words, the replication line (indicated by the curved arrows in the diagram) directly connects all SQL nodes used as sources and replicas. </p> <p> It should also be possible to set up circular replication in which not all source SQL nodes are also replicas, as shown here: </p> <div class="figure"> <a name="fig-mysql-cluster-circular-not-all-sources-replicas"> </a> <p class="title"> <b> Figure 25.12 NDB Cluster Circular Replication Where Not All Sources Are Replicas </b> </p> <div class="figure-contents"> <div class="mediaobject"> <img alt="Some content is described in the surrounding text. The diagram shows three clusters, each with two nodes. Arrows connecting SQL nodes in different clusters illustrate that not all sources are replicas." src="images/cluster-circular-replication-2.png" style="width: 100%; max-width: 542px;"/> </div> </div> </div> <br class="figure-break"/> <p> In this case, different SQL nodes in each cluster are used as sources and replicas. However, you must <span class="emphasis"> <em> not </em> </span> start any of the SQL nodes with the <a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates"> <code class="literal"> log_replica_updates </code> </a> system variable enabled. This type of circular replication scheme for NDB Cluster, in which the line of replication (again indicated by the curved arrows in the diagram) is discontinuous, should be possible, but it should be noted that it has not yet been thoroughly tested and must therefore still be considered experimental. </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> The <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> storage engine uses <span class="firstterm"> idempotent execution mode </span> , which suppresses duplicate-key and other errors that otherwise break circular replication of NDB Cluster. This is equivalent to setting the global value of the system variable <a class="link" href="replication-options-replica.html#sysvar_replica_exec_mode"> <code class="literal"> replica_exec_mode </code> </a> to <code class="literal"> IDEMPOTENT </code> , although this is not necessary in NDB Cluster replication, since NDB Cluster sets this variable automatically and ignores any attempts to set it explicitly. </p> </div> <p> <b> NDB Cluster replication and primary keys. </b> <a class="indexterm" name="idm46045086677184"> </a> In the event of a node failure, errors in replication of <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> tables without primary keys can still occur, due to the possibility of duplicate rows being inserted in such cases. For this reason, it is highly recommended that all <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> tables being replicated have explicit primary keys. </p> <p> <b> NDB Cluster Replication and Unique Keys. </b> <a class="indexterm" name="idm46045086671824"> </a> In older versions of NDB Cluster, operations that updated values of unique key columns of <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> tables could result in duplicate-key errors when replicated. This issue is solved for replication between <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> tables by deferring unique key checks until after all table row updates have been performed. </p> <p> Deferring constraints in this way is currently supported only by <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> . Thus, updates of unique keys when replicating from <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> to a different storage engine such as <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine"> <code class="literal"> InnoDB </code> </a> or <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine"> <code class="literal"> MyISAM </code> </a> are still not supported. </p> <p> The problem encountered when replicating without deferred checking of unique key updates can be illustrated using <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> table such as <code class="literal"> t </code> , is created and populated on the source (and transmitted to a replica that does not support deferred unique key updates) as shown here: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa22455322"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t <span class="token punctuation">(</span> p <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">,</span> c <span class="token datatype">INT</span><span class="token punctuation">,</span> <span class="token keyword">UNIQUE</span> <span class="token keyword">KEY</span> u <span class="token punctuation">(</span>c<span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token keyword">ENGINE</span> <span class="token keyword">NDB</span><span class="token punctuation">;</span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">,</span><span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">,</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre> </div> <p> The following <a class="link" href="update.html" title="15.2.17 UPDATE Statement"> <code class="literal"> UPDATE </code> </a> statement on <code class="literal"> t </code> succeeds on the source, since the rows affected are processed in the order determined by the <code class="literal"> ORDER BY </code> option, performed over the entire table: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa24553388"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">UPDATE</span> t <span class="token keyword">SET</span> c <span class="token operator">=</span> c <span class="token operator">-</span> <span class="token number">1</span> <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> p<span class="token punctuation">;</span></code></pre> </div> <p> The same statement fails with a duplicate key error or other constraint violation on the replica, because the ordering of the row updates is performed for one partition at a time, rather than for the table as a whole. </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> Every <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> table is implicitly partitioned by key when it is created. See <a class="xref" href="partitioning-key.html" title="26.2.5 KEY Partitioning"> Section 26.2.5, “KEY Partitioning” </a> , for more information. </p> </div> <p> <b> GTIDs not supported. </b> Replication using global transaction IDs is not compatible with the <code class="literal"> NDB </code> storage engine, and is not supported. Enabling GTIDs is likely to cause NDB Cluster Replication to fail. </p> <p> <b> Restarting with --initial. </b> <a class="indexterm" name="idm46045086647744"> </a> Restarting the cluster with the <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_initial"> <code class="option"> --initial </code> </a> option causes the sequence of GCI and epoch numbers to start over from <code class="literal"> 0 </code> . (This is generally true of NDB Cluster and not limited to replication scenarios involving Cluster.) The MySQL servers involved in replication should in this case be restarted. After this, you should use the <a class="link" href="reset-binary-logs-and-gtids.html" title="15.4.1.2 RESET BINARY LOGS AND GTIDS Statement"> <code class="literal"> RESET BINARY LOGS AND GTIDS </code> </a> and <a class="link" href="reset-replica.html" title="15.4.2.3 RESET REPLICA Statement"> <code class="literal"> RESET REPLICA </code> </a> statements to clear the invalid <code class="literal"> ndb_binlog_index </code> and <code class="literal"> ndb_apply_status </code> tables, respectively. </p> <p> <a name="mysql-cluster-replication-ndb-to-non-ndb"> </a> <b> Replication from NDB to other storage engines. </b> It is possible to replicate an <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> table on the source to a table using a different storage engine on the replica, taking into account the restrictions listed here: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> Multi-source and circular replication are not supported (tables on both the source and the replica must use the <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> storage engine for this to work). </p> </li> <li class="listitem"> <p> Using a storage engine which does not perform binary logging for tables on the replica requires special handling. </p> </li> <li class="listitem"> <p> Use of a nontransactional storage engine for tables on the replica also requires special handling. </p> </li> <li class="listitem"> <p> The source <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server"> <span class="command"> <strong> mysqld </strong> </span> </a> must be started with <a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-as-write"> <code class="option"> --ndb-log-update-as-write=0 </code> </a> or <code class="option"> --ndb-log-update-as-write=OFF </code> . </p> </li> </ul> </div> <p> The next few paragraphs provide additional information about each of the issues just described. </p> <p> <b> Multiple sources not supported when replicating NDB to other storage engines. </b> For replication from <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> to a different storage engine, the relationship between the two databases must be one-to-one. This means that bidirectional or circular replication is not supported between NDB Cluster and other storage engines. </p> <p> In addition, it is not possible to configure more than one replication channel when replicating between <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> and a different storage engine. (An NDB Cluster database <span class="emphasis"> <em> can </em> </span> simultaneously replicate to multiple NDB Cluster databases.) If the source uses <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> tables, it is still possible to have more than one MySQL Server maintain a binary log of all changes, but for the replica to change sources (fail over), the new source-replica relationship must be explicitly defined on the replica. </p> <p> <b> Replicating NDB tables to a storage engine that does not perform binary logging. </b> <a class="indexterm" name="idm46045086621024"> </a> If you attempt to replicate from an NDB Cluster to a replica that uses a storage engine that does not handle its own binary logging, the replication process aborts with the error <span class="errortext"> Binary logging not possible ... Statement cannot be written atomically since more than one engine involved and at least one engine is self-logging </span> (Error <span class="errorcode"> 1595 </span> ). It is possible to work around this issue in one of the following ways: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <b> Turn off binary logging on the replica. </b> This can be accomplished by setting <a class="link" href="replication-options-binary-log.html#sysvar_sql_log_bin"> <code class="literal"> sql_log_bin = 0 </code> </a> . </p> </li> <li class="listitem"> <p> <b> Change the storage engine used for the mysql.ndb_apply_status table. </b> Causing this table to use an engine that does not handle its own binary logging can also eliminate the conflict. This can be done by issuing a statement such as <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE mysql.ndb_apply_status ENGINE=MyISAM </code> </a> on the replica. It is safe to do this when using a storage engine other than <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> on the replica, since you do not need to worry about keeping multiple replicas synchronized. </p> </li> <li class="listitem"> <p> <b> Filter out changes to the mysql.ndb_apply_status table on the replica. </b> This can be done by starting the replica with <a class="link" href="replication-options-replica.html#option_mysqld_replicate-ignore-table"> <code class="option"> --replicate-ignore-table=mysql.ndb_apply_status </code> </a> . If you need for other tables to be ignored by replication, you might wish to use an appropriate <a class="link" href="replication-options-replica.html#option_mysqld_replicate-wild-ignore-table"> <code class="option"> --replicate-wild-ignore-table </code> </a> option instead. </p> </li> </ul> </div> <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Important </div> <p> You should <span class="emphasis"> <em> not </em> </span> disable replication or binary logging of <code class="literal"> mysql.ndb_apply_status </code> or change the storage engine used for this table when replicating from one NDB Cluster to another. See <a class="xref" href="mysql-cluster-replication-issues.html#mysql-cluster-replication-issues-filtering" title="Replication and binary log filtering rules with replication between NDB Clusters"> Replication and binary log filtering rules with replication between NDB Clusters </a> , for details. </p> </div> <p> <a name="mysql-cluster-replication-ndb-to-nontransactional"> </a> <b> Replication from NDB to a nontransactional storage engine. </b> When replicating from <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> to a nontransactional storage engine such as <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine"> <code class="literal"> MyISAM </code> </a> , you may encounter unnecessary duplicate key errors when replicating <a class="link" href="insert-on-duplicate.html" title="15.2.7.2 INSERT ... ON DUPLICATE KEY UPDATE Statement"> <code class="literal"> INSERT ... ON DUPLICATE KEY UPDATE </code> </a> statements. You can suppress these by using <a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-as-write"> <code class="option"> --ndb-log-update-as-write=0 </code> </a> , which forces updates to be logged as writes, rather than as updates. </p> <p> <a name="mysql-cluster-replication-issues-tde"> </a> <b> NDB Replication and File System Encryption (TDE). </b> The use of an encrypted filesystem does not have any effect on NDB Replication. All of the following scenarios are supported: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> Replication of an NDB Cluster having an encrypted file system to an NDB Cluster whose file system is not encrypted. </p> </li> <li class="listitem"> <p> Replication of an NDB Cluster whose file system is not encrypted to an NDB Cluster whose file system is encrypted. </p> </li> <li class="listitem"> <p> Replication of an NDB Cluster whose file system is encrypted to a standalone MySQL server using <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine"> <code class="literal"> InnoDB </code> </a> tables which are not encrypted. </p> </li> <li class="listitem"> <p> Replication of an NDB Cluster with an unencrypted file system to a standalone MySQL server using <code class="literal"> InnoDB </code> tables with file sytem encryption. </p> </li> </ul> </div> <p> <a name="mysql-cluster-replication-issues-filtering"> </a> <b> Replication and binary log filtering rules with replication between NDB Clusters. </b> If you are using any of the options <code class="option"> --replicate-do-* </code> , <code class="option"> --replicate-ignore-* </code> , <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db </code> </a> , or <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db"> <code class="option"> --binlog-ignore-db </code> </a> to filter databases or tables being replicated, you must take care not to block replication or binary logging of the <code class="literal"> mysql.ndb_apply_status </code> , which is required for replication between NDB Clusters to operate properly. In particular, you must keep in mind the following: </p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p> Using <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-db"> <code class="option"> --replicate-do-db= <em class="replaceable"> <code> db_name </code> </em> </code> </a> (and no other <code class="option"> --replicate-do-* </code> or <code class="option"> --replicate-ignore-* </code> options) means that <span class="emphasis"> <em> only </em> </span> tables in database <em class="replaceable"> <code> db_name </code> </em> are replicated. In this case, you should also use <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-db"> <code class="option"> --replicate-do-db=mysql </code> </a> , <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db=mysql </code> </a> , or <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-table"> <code class="option"> --replicate-do-table=mysql.ndb_apply_status </code> </a> to ensure that <code class="literal"> mysql.ndb_apply_status </code> is populated on replicas. </p> <p> Using <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db= <em class="replaceable"> <code> db_name </code> </em> </code> </a> (and no other <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db </code> </a> options) means that changes <span class="emphasis"> <em> only </em> </span> to tables in database <em class="replaceable"> <code> db_name </code> </em> are written to the binary log. In this case, you should also use <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-db"> <code class="option"> --replicate-do-db=mysql </code> </a> , <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db=mysql </code> </a> , or <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-table"> <code class="option"> --replicate-do-table=mysql.ndb_apply_status </code> </a> to ensure that <code class="literal"> mysql.ndb_apply_status </code> is populated on replicas. </p> </li> <li class="listitem"> <p> Using <a class="link" href="replication-options-replica.html#option_mysqld_replicate-ignore-db"> <code class="option"> --replicate-ignore-db=mysql </code> </a> means that no tables in the <code class="literal"> mysql </code> database are replicated. In this case, you should also use <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-table"> <code class="option"> --replicate-do-table=mysql.ndb_apply_status </code> </a> to ensure that <code class="literal"> mysql.ndb_apply_status </code> is replicated. </p> <p> Using <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db"> <code class="option"> --binlog-ignore-db=mysql </code> </a> means that no changes to tables in the <code class="literal"> mysql </code> database are written to the binary log. In this case, you should also use <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-table"> <code class="option"> --replicate-do-table=mysql.ndb_apply_status </code> </a> to ensure that <code class="literal"> mysql.ndb_apply_status </code> is replicated. </p> </li> </ol> </div> <p> You should also remember that each replication rule requires the following: </p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p> Its own <code class="option"> --replicate-do-* </code> or <code class="option"> --replicate-ignore-* </code> option, and that multiple rules cannot be expressed in a single replication filtering option. For information about these rules, see <a class="xref" href="replication-options.html" title="19.1.6 Replication and Binary Logging Options and Variables"> Section 19.1.6, “Replication and Binary Logging Options and Variables” </a> . </p> </li> <li class="listitem"> <p> Its own <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db </code> </a> or <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db"> <code class="option"> --binlog-ignore-db </code> </a> option, and that multiple rules cannot be expressed in a single binary log filtering option. For information about these rules, see <a class="xref" href="binary-log.html" title="7.4.4 The Binary Log"> Section 7.4.4, “The Binary Log” </a> . </p> </li> </ol> </div> <p> If you are replicating an NDB Cluster to a replica that uses a storage engine other than <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> , the considerations just given previously may not apply, as discussed elsewhere in this section. </p> <p> <a name="mysql-cluster-replication-ipv6"> </a> <b> NDB Cluster Replication and IPv6. </b> All types of NDB Cluster nodes support IPv6 in NDB 8.4; this includes management nodes, data nodes, and API or SQL nodes. </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> In NDB 8.4, you can disable IPv6 support in the Linux kernel if you do not intend to use IPv6 addressing for any NDB Cluster nodes. </p> </div> <p> <b> Attribute promotion and demotion. </b> NDB Cluster Replication includes support for attribute promotion and demotion. The implementation of the latter distinguishes between lossy and non-lossy type conversions, and their use on the replica can be controlled by setting the global value of the system variable <a class="link" href="replication-options-replica.html#sysvar_replica_type_conversions"> <code class="literal"> replica_type_conversions </code> </a> . </p> <p> For more information about attribute promotion and demotion in NDB Cluster, see <a class="xref" href="replication-features-differing-tables.html#replication-features-attribute-promotion" title="Row-based replication: attribute promotion and demotion"> Row-based replication: attribute promotion and demotion </a> . </p> <p> <code class="literal"> NDB </code> , unlike <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine"> <code class="literal"> InnoDB </code> </a> or <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine"> <code class="literal"> MyISAM </code> </a> , does not write changes to virtual columns to the binary log; however, this has no detrimental effects on NDB Cluster Replication or replication between <code class="literal"> NDB </code> and other storage engines. Changes to stored generated columns are logged. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/telemetry-metrics.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="telemetry-metrics"> </a> 35.4 OpenTelemetry Metrics </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <span class="section"> <a href="telemetry-metrics-configuration.html"> 35.4.1 Configuring Metrics Telemetry </a> </span> </dt> <dt> <span class="section"> <a href="telemetry-metrics-meters.html"> 35.4.2 Server Meters </a> </span> </dt> <dt> <span class="section"> <a href="telemetry-metrics-meter-metrics.html"> 35.4.3 Server Metrics </a> </span> </dt> </dl> </div> <p> The Server Telemetry Metrics Service and the Server Metrics Instrument Service enable you to register and query telemetry meters, metrics, and metric measurements, in order to periodically export these measurements using the OpenTelemetry protocol. </p> <p> For more information on these services, see Server Telemetry Metrics Service and the Server Metrics Instrument Service documentation in the MySQL Server Doxygen Documentation. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-hwinfo.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysql-cluster-ndbinfo-hwinfo"> </a> 25.6.17.39 The ndbinfo hwinfo Table </h4> </div> </div> </div> <a class="indexterm" name="idm46045089150512"> </a> <p> The <code class="literal"> hwinfo </code> table provides information about the hardware on which a given data node executes. </p> <p> The <code class="literal"> hwinfo </code> table contains the following columns: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> node_id </code> </p> <p> Node ID </p> </li> <li class="listitem"> <p> <code class="literal"> cpu_cnt_max </code> </p> <p> Number of processors on this host </p> </li> <li class="listitem"> <p> <code class="literal"> cpu_cnt </code> </p> <p> Number of processors available to this node </p> </li> <li class="listitem"> <p> <code class="literal"> num_cpu_cores </code> </p> <p> Number of CPU cores on this host </p> </li> <li class="listitem"> <p> <code class="literal"> num_cpu_sockets </code> </p> <p> Number of CPU sockets on this host </p> </li> <li class="listitem"> <p> <code class="literal"> HW_memory_size </code> </p> <p> Amount of memory available on this host </p> </li> <li class="listitem"> <p> <code class="literal"> model_name </code> </p> <p> CPU model name </p> </li> </ul> </div> <h5> <a name="idm46045089132880"> </a> Notes </h5> <p> The <code class="literal"> hwinfo </code> table is available on all operating systems supported by <code class="literal"> NDB </code> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/what-is-crashing.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="what-is-crashing"> </a> B.3.1 How to Determine What Is Causing a Problem </h3> </div> </div> </div> <p> When you run into a problem, the first thing you should do is to find out which program or piece of equipment is causing it: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> If you have one of the following symptoms, then it is probably a hardware problems (such as memory, motherboard, CPU, or hard disk) or kernel problem: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> The keyboard does not work. This can normally be checked by pressing the Caps Lock key. If the Caps Lock light does not change, you have to replace your keyboard. (Before doing this, you should try to restart your computer and check all cables to the keyboard.) </p> </li> <li class="listitem"> <p> The mouse pointer does not move. </p> </li> <li class="listitem"> <p> The machine does not answer to a remote machine's pings. </p> </li> <li class="listitem"> <p> Other programs that are not related to MySQL do not behave correctly. </p> </li> <li class="listitem"> <p> Your system restarted unexpectedly. (A faulty user-level program should never be able to take down your system.) </p> </li> </ul> </div> <p> In this case, you should start by checking all your cables and run some diagnostic tool to check your hardware! You should also check whether there are any patches, updates, or service packs for your operating system that could likely solve your problem. Check also that all your libraries (such as <code class="literal"> glibc </code> ) are up to date. </p> <p> It is always good to use a machine with ECC memory to discover memory problems early. </p> </li> <li class="listitem"> <p> If your keyboard is locked up, you may be able to recover by logging in to your machine from another machine and executing <code class="literal"> kbd_mode -a </code> . </p> </li> <li class="listitem"> <p> Please examine your system log file ( <code class="filename"> /var/log/messages </code> or similar) for reasons for your problem. If you think the problem is in MySQL, you should also examine MySQL's log files. See <a class="xref" href="server-logs.html" title="7.4 MySQL Server Logs"> Section 7.4, “MySQL Server Logs” </a> . </p> </li> <li class="listitem"> <p> If you do not think you have hardware problems, you should try to find out which program is causing problems. Try using <span class="command"> <strong> top </strong> </span> , <span class="command"> <strong> ps </strong> </span> , Task Manager, or some similar program, to check which program is taking all CPU or is locking the machine. </p> </li> <li class="listitem"> <p> Use <span class="command"> <strong> top </strong> </span> , <span class="command"> <strong> df </strong> </span> , or a similar program to check whether you are out of memory, disk space, file descriptors, or some other critical resource. </p> </li> <li class="listitem"> <p> If the problem is some runaway process, you can always try to kill it. If it does not want to die, there is probably a bug in the operating system. </p> </li> </ul> </div> <p> If you have examined all other possibilities and concluded that the MySQL server or a MySQL client is causing the problem, it is time to create a bug report, see <a class="xref" href="bug-reports.html" title="1.6 How to Report Bugs or Problems"> Section 1.6, “How to Report Bugs or Problems” </a> . In the bug report, try to give a complete description of how the system is behaving and what you think is happening. Also state why you think that MySQL is causing the problem. Take into consideration all the situations described in this chapter. State any problems exactly how they appear when you examine your system. Use the <span class="quote"> “ <span class="quote"> copy and paste </span> ” </span> method for any output and error messages from programs and log files. </p> <p> Try to describe in detail which program is not working and all symptoms you see. We have in the past received many bug reports that state only <span class="quote"> “ <span class="quote"> the system does not work. </span> ” </span> This provides us with no information about what could be the problem. </p> <p> If a program fails, it is always useful to know the following information: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> Has the program in question made a segmentation fault (did it dump core)? </p> </li> <li class="listitem"> <p> Is the program taking up all available CPU time? Check with <span class="command"> <strong> top </strong> </span> . Let the program run for a while, it may simply be evaluating something computationally intensive. </p> </li> <li class="listitem"> <p> If the <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server"> <span class="command"> <strong> mysqld </strong> </span> </a> server is causing problems, can you get any response from it with <a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program"> <span class="command"> <strong> mysqladmin -u root ping </strong> </span> </a> or <a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program"> <span class="command"> <strong> mysqladmin -u root processlist </strong> </span> </a> ? </p> </li> <li class="listitem"> <p> What does a client program say when you try to connect to the MySQL server? (Try with <a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client"> <span class="command"> <strong> mysql </strong> </span> </a> , for example.) Does the client jam? Do you get any output from the program? </p> </li> </ul> </div> <p> When sending a bug report, you should follow the outline described in <a class="xref" href="bug-reports.html" title="1.6 How to Report Bugs or Problems"> Section 1.6, “How to Report Bugs or Problems” </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/gis-general-property-functions.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="gis-general-property-functions"> </a> 14.16.7.1 General Geometry Property Functions </h4> </div> </div> </div> <p> The functions listed in this section do not restrict their argument and accept a geometry value of any type. </p> <p> Unless otherwise specified, functions in this section handle their geometry arguments as follows: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> If any argument is <code class="literal"> NULL </code> , the return value is <code class="literal"> NULL </code> . </p> </li> <li class="listitem"> <p> If any geometry argument is not a syntactically well-formed geometry, an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_gis_invalid_data" target="_top"> <code class="literal"> ER_GIS_INVALID_DATA </code> </a> error occurs. </p> </li> <li class="listitem"> <p> If any geometry argument is a syntactically well-formed geometry in an undefined spatial reference system (SRS), an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_srs_not_found" target="_top"> <code class="literal"> ER_SRS_NOT_FOUND </code> </a> error occurs. </p> </li> <li class="listitem"> <p> If any SRID argument is not within the range of a 32-bit unsigned integer, an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_data_out_of_range" target="_top"> <code class="literal"> ER_DATA_OUT_OF_RANGE </code> </a> error occurs. </p> </li> <li class="listitem"> <p> If any SRID argument refers to an undefined SRS, an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_srs_not_found" target="_top"> <code class="literal"> ER_SRS_NOT_FOUND </code> </a> error occurs. </p> </li> <li class="listitem"> <p> Otherwise, the return value is non- <code class="literal"> NULL </code> . </p> </li> </ul> </div> <p> These functions are available for obtaining geometry properties: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <a name="function_st-dimension"> </a> <p> <a class="link" href="gis-general-property-functions.html#function_st-dimension"> <code class="literal"> ST_Dimension( <em class="replaceable"> <code> g </code> </em> ) </code> </a> </p> <a class="indexterm" name="idm46045197547632"> </a> <p> Returns the inherent dimension of the geometry value <em class="replaceable"> <code> g </code> </em> . The dimension can be −1, 0, 1, or 2. The meaning of these values is given in <a class="xref" href="gis-class-geometry.html" title="13.4.2.2 Geometry Class"> Section 13.4.2.2, “Geometry Class” </a> . </p> <p> <a class="link" href="gis-general-property-functions.html#function_st-dimension"> <code class="literal"> ST_Dimension() </code> </a> handles its arguments as described in the introduction to this section. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa54369554"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Dimension</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LineString(1 1,2 2)'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> ST_Dimension(ST_GeomFromText('LineString(1 1,2 2)')) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 1 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> </li> <li class="listitem"> <a name="function_st-envelope"> </a> <p> <a class="link" href="gis-general-property-functions.html#function_st-envelope"> <code class="literal"> ST_Envelope( <em class="replaceable"> <code> g </code> </em> ) </code> </a> </p> <a class="indexterm" name="idm46045197535264"> </a> <p> Returns the minimum bounding rectangle (MBR) for the geometry value <em class="replaceable"> <code> g </code> </em> . The result is returned as a <code class="literal"> Polygon </code> value that is defined by the corner points of the bounding box: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa23466958"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token function">POLYGON</span><span class="token punctuation">(</span><span class="token punctuation">(</span>MINX MINY<span class="token punctuation">,</span> MAXX MINY<span class="token punctuation">,</span> MAXX MAXY<span class="token punctuation">,</span> MINX MAXY<span class="token punctuation">,</span> MINX MINY<span class="token punctuation">)</span><span class="token punctuation">)</span></code></pre> </div> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46018837"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_AsText</span><span class="token punctuation">(</span><span class="token function">ST_Envelope</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LineString(1 1,2 2)'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> ST_AsText(ST_Envelope(ST_GeomFromText('LineString(1 1,2 2)'))) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> POLYGON((1 1,2 1,2 2,1 2,1 1)) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> <p> If the argument is a point or a vertical or horizontal line segment, <a class="link" href="gis-general-property-functions.html#function_st-envelope"> <code class="literal"> ST_Envelope() </code> </a> returns the point or the line segment as its MBR rather than returning an invalid polygon: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa82926961"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_AsText</span><span class="token punctuation">(</span><span class="token function">ST_Envelope</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LineString(1 1,1 2)'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> ST_AsText(ST_Envelope(ST_GeomFromText('LineString(1 1,1 2)'))) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> LINESTRING(1 1,1 2) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> <p> <a class="link" href="gis-general-property-functions.html#function_st-envelope"> <code class="literal"> ST_Envelope() </code> </a> handles its arguments as described in the introduction to this section, with this exception: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> If the geometry has an SRID value for a geographic spatial reference system (SRS), an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_not_implemented_for_geographic_srs" target="_top"> <code class="literal"> ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS </code> </a> error occurs. </p> </li> </ul> </div> </li> <li class="listitem"> <a name="function_st-geometrytype"> </a> <p> <a class="link" href="gis-general-property-functions.html#function_st-geometrytype"> <code class="literal"> ST_GeometryType( <em class="replaceable"> <code> g </code> </em> ) </code> </a> </p> <a class="indexterm" name="idm46045197515872"> </a> <p> Returns a binary string indicating the name of the geometry type of which the geometry instance <em class="replaceable"> <code> g </code> </em> is a member. The name corresponds to one of the instantiable <code class="literal"> Geometry </code> subclasses. </p> <p> <a class="link" href="gis-general-property-functions.html#function_st-geometrytype"> <code class="literal"> ST_GeometryType() </code> </a> handles its arguments as described in the introduction to this section. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa1317378"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_GeometryType</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'POINT(1 1)'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> ST_GeometryType(ST_GeomFromText('POINT(1 1)')) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> POINT <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> </li> <li class="listitem"> <a name="function_st-isempty"> </a> <p> <a class="link" href="gis-general-property-functions.html#function_st-isempty"> <code class="literal"> ST_IsEmpty( <em class="replaceable"> <code> g </code> </em> ) </code> </a> </p> <a class="indexterm" name="idm46045197503600"> </a> <p> This function is a placeholder that returns 1 for an empty geometry collection value or 0 otherwise. </p> <p> The only valid empty geometry is represented in the form of an empty geometry collection value. MySQL does not support GIS <code class="literal"> EMPTY </code> values such as <code class="literal"> POINT EMPTY </code> . </p> <p> <a class="link" href="gis-general-property-functions.html#function_st-isempty"> <code class="literal"> ST_IsEmpty() </code> </a> handles its arguments as described in the introduction to this section. </p> </li> <li class="listitem"> <a name="function_st-issimple"> </a> <p> <a class="link" href="gis-general-property-functions.html#function_st-issimple"> <code class="literal"> ST_IsSimple( <em class="replaceable"> <code> g </code> </em> ) </code> </a> </p> <a class="indexterm" name="idm46045197493008"> </a> <p> Returns 1 if the geometry value <em class="replaceable"> <code> g </code> </em> is simple according to the ISO <em class="citetitle"> SQL/MM Part 3: Spatial </em> standard. <a class="link" href="gis-general-property-functions.html#function_st-issimple"> <code class="literal"> ST_IsSimple() </code> </a> returns 0 if the argument is not simple. </p> <p> The descriptions of the instantiable geometric classes given under <a class="xref" href="opengis-geometry-model.html" title="13.4.2 The OpenGIS Geometry Model"> Section 13.4.2, “The OpenGIS Geometry Model” </a> include the specific conditions that cause class instances to be classified as not simple. </p> <p> <a class="link" href="gis-general-property-functions.html#function_st-issimple"> <code class="literal"> ST_IsSimple() </code> </a> handles its arguments as described in the introduction to this section, with this exception: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> If the geometry has a geographic SRS with a longitude or latitude that is out of range, an error occurs: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: square; "> <li class="listitem"> <p> If a longitude value is not in the range (−180, 180], an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_geometry_param_longitude_out_of_range" target="_top"> <code class="literal"> ER_GEOMETRY_PARAM_LONGITUDE_OUT_OF_RANGE </code> </a> error occurs. </p> </li> <li class="listitem"> <p> If a latitude value is not in the range [−90, 90], an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_geometry_param_latitude_out_of_range" target="_top"> <code class="literal"> ER_GEOMETRY_PARAM_LATITUDE_OUT_OF_RANGE </code> </a> error occurs. </p> </li> </ul> </div> <p> Ranges shown are in degrees. The exact range limits deviate slightly due to floating-point arithmetic. </p> </li> </ul> </div> </li> <li class="listitem"> <a name="function_st-srid"> </a> <p> <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID( <em class="replaceable"> <code> g </code> </em> [, <em class="replaceable"> <code> srid </code> </em> ]) </code> </a> </p> <a class="indexterm" name="idm46045197473632"> </a> <p> With a single argument representing a valid geometry object <em class="replaceable"> <code> g </code> </em> , <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> returns an integer indicating the ID of the spatial reference system (SRS) associated with <em class="replaceable"> <code> g </code> </em> . </p> <p> With the optional second argument representing a valid SRID value, <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> returns an object with the same type as its first argument with an SRID value equal to the second argument. This only sets the SRID value of the object; it does not perform any transformation of coordinate values. </p> <p> <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> handles its arguments as described in the introduction to this section, with this exception: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> For the single-argument syntax, <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> returns the geometry SRID even if it refers to an undefined SRS. An <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_srs_not_found" target="_top"> <code class="literal"> ER_SRS_NOT_FOUND </code> </a> error does not occur. </p> </li> </ul> </div> <p> <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID( <em class="replaceable"> <code> g </code> </em> , <em class="replaceable"> <code> target_srid </code> </em> ) </code> </a> and <a class="link" href="spatial-operator-functions.html#function_st-transform"> <code class="literal"> ST_Transform( <em class="replaceable"> <code> g </code> </em> , <em class="replaceable"> <code> target_srid </code> </em> ) </code> </a> differ as follows: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> changes the geometry SRID value without transforming its coordinates. </p> </li> <li class="listitem"> <p> <a class="link" href="spatial-operator-functions.html#function_st-transform"> <code class="literal"> ST_Transform() </code> </a> transforms the geometry coordinates in addition to changing its SRID value. </p> </li> </ul> </div> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa74861556"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@g</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LineString(1 1,2 2)'</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_SRID</span><span class="token punctuation">(</span><span class="token variable">@g</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> ST_SRID(@g) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 0 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@g</span> <span class="token operator">=</span> <span class="token function">ST_SRID</span><span class="token punctuation">(</span><span class="token variable">@g</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_SRID</span><span class="token punctuation">(</span><span class="token variable">@g</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> ST_SRID(@g) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 4326 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> <p> It is possible to create a geometry in a particular SRID by passing to <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> the result of one of the MySQL-specific functions for creating spatial values, along with an SRID value. For example: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa77323920"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@g1</span> <span class="token operator">=</span> <span class="token function">ST_SRID</span><span class="token punctuation">(</span><span class="token function">Point</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre> </div> <p> However, that method creates the geometry in SRID 0, then casts it to SRID 4326 (WGS 84). A preferable alternative is to create the geometry with the correct spatial reference system to begin with. For example: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa77913484"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@g1</span> <span class="token operator">=</span> <span class="token function">ST_PointFromText</span><span class="token punctuation">(</span><span class="token string">'POINT(1 1)'</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">SET</span> <span class="token variable">@g1</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'POINT(1 1)'</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre> </div> <p> The two-argument form of <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> is useful for tasks such as correcting or changing the SRS of geometries that have an incorrect SRID. </p> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/savepoint.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="savepoint"> </a> 15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements </h3> </div> </div> </div> <a class="indexterm" name="idm46045178627760"> </a> <a class="indexterm" name="idm46045178626720"> </a> <a class="indexterm" name="idm46045178625648"> </a> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa66696333"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SAVEPOINT</span> <em class="replaceable">identifier</em> <span class="token keyword">ROLLBACK</span> <span class="token punctuation">[</span><span class="token keyword">WORK</span><span class="token punctuation">]</span> <span class="token keyword">TO</span> <span class="token punctuation">[</span><span class="token keyword">SAVEPOINT</span><span class="token punctuation">]</span> <em class="replaceable">identifier</em> <span class="token keyword">RELEASE</span> <span class="token keyword">SAVEPOINT</span> <em class="replaceable">identifier</em></code></pre> </div> <p> <code class="literal"> InnoDB </code> supports the SQL statements <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> SAVEPOINT </code> </a> , <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> ROLLBACK TO SAVEPOINT </code> </a> , <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> RELEASE SAVEPOINT </code> </a> and the optional <code class="literal"> WORK </code> keyword for <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements"> <code class="literal"> ROLLBACK </code> </a> . </p> <p> The <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> SAVEPOINT </code> </a> statement sets a named transaction savepoint with a name of <em class="replaceable"> <code> identifier </code> </em> . If the current transaction has a savepoint with the same name, the old savepoint is deleted and a new one is set. </p> <p> The <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> ROLLBACK TO SAVEPOINT </code> </a> statement rolls back a transaction to the named savepoint without terminating the transaction. Modifications that the current transaction made to rows after the savepoint was set are undone in the rollback, but <code class="literal"> InnoDB </code> does <span class="emphasis"> <em> not </em> </span> release the row locks that were stored in memory after the savepoint. (For a new inserted row, the lock information is carried by the transaction ID stored in the row; the lock is not separately stored in memory. In this case, the row lock is released in the undo.) Savepoints that were set at a later time than the named savepoint are deleted. </p> <p> If the <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> ROLLBACK TO SAVEPOINT </code> </a> statement returns the following error, it means that no savepoint with the specified name exists: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-none"><div class="docs-select-all right" id="sa17695036"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">ERROR 1305 (42000): SAVEPOINT <em class="replaceable">identifier</em> does not exist</code></pre> </div> <p> The <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> RELEASE SAVEPOINT </code> </a> statement removes the named savepoint from the set of savepoints of the current transaction. No commit or rollback occurs. It is an error if the savepoint does not exist. </p> <p> All savepoints of the current transaction are deleted if you execute a <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements"> <code class="literal"> COMMIT </code> </a> , or a <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements"> <code class="literal"> ROLLBACK </code> </a> that does not name a savepoint. </p> <p> A new savepoint level is created when a stored function is invoked or a trigger is activated. The savepoints on previous levels become unavailable and thus do not conflict with savepoints on the new level. When the function or trigger terminates, any savepoints it created are released and the previous savepoint level is restored. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-quick.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="mysql-cluster-quick"> </a> 25.4.1 Quick Test Setup of NDB Cluster </h3> </div> </div> </div> <a class="indexterm" name="idm46045122003648"> </a> <a class="indexterm" name="idm46045122002192"> </a> <a class="indexterm" name="idm46045122000704"> </a> <p> To familiarize you with the basics, we describe the simplest possible configuration for a functional NDB Cluster. After this, you should be able to design your desired setup from the information provided in the other relevant sections of this chapter. </p> <p> First, you need to create a configuration directory such as <code class="filename"> /var/lib/mysql-cluster </code> , by executing the following command as the system <code class="literal"> root </code> user: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa96211790"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mkdir</span> /var/lib/mysql-cluster</code></pre> </div> <p> In this directory, create a file named <code class="filename"> config.ini </code> that contains the following information. Substitute appropriate values for <code class="literal"> HostName </code> and <code class="literal"> DataDir </code> as necessary for your system. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa82302769"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token comment" spellcheck="true"># file "config.ini" - showing minimal setup consisting of 1 data node,</span> <span class="token comment" spellcheck="true"># 1 management server, and 3 MySQL servers.</span> <span class="token comment" spellcheck="true"># The empty default sections are not required, and are shown only for</span> <span class="token comment" spellcheck="true"># the sake of completeness.</span> <span class="token comment" spellcheck="true"># Data nodes must provide a hostname but MySQL Servers are not required</span> <span class="token comment" spellcheck="true"># to do so.</span> <span class="token comment" spellcheck="true"># If you do not know the hostname for your machine, use localhost.</span> <span class="token comment" spellcheck="true"># The DataDir parameter also has a default value, but it is recommended to</span> <span class="token comment" spellcheck="true"># set it explicitly.</span> <span class="token comment" spellcheck="true"># [api] and [mgm] are aliases for [mysqld] and [ndb_mgmd], respectively.</span> <span class="token selector">[ndbd default]</span> <span class="token constant">NoOfReplicas</span><span class="token attr-value"><span class="token punctuation">=</span> 1</span> <span class="token selector">[mysqld default]</span> <span class="token selector">[ndb_mgmd default]</span> <span class="token selector">[tcp default]</span> <span class="token selector">[ndb_mgmd]</span> <span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span> myhost.example.com</span> <span class="token selector">[ndbd]</span> <span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span> myhost.example.com</span> <span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span> /var/lib/mysql-cluster</span> <span class="token selector">[mysqld]</span> <span class="token selector">[mysqld]</span> <span class="token selector">[mysqld]</span></code></pre> </div> <p> You can now start the <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> management server. By default, it attempts to read the <code class="filename"> config.ini </code> file in its current working directory, so change location into the directory where the file is located and then invoke <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> : </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa70209928"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">cd</span> /var/lib/mysql-cluster <span class="token prompt">$> </span><span class="token command">ndb_mgmd</span></code></pre> </div> <p> Then start a single data node by running <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> <span class="command"> <strong> ndbd </strong> </span> </a> : </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa39743877"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">ndbd</span></code></pre> </div> <p> By default, <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> <span class="command"> <strong> ndbd </strong> </span> </a> looks for the management server at <code class="literal"> localhost </code> on port 1186. </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> If you have installed MySQL from a binary tarball, you must to specify the path of the <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> <span class="command"> <strong> ndb_mgmd </strong> </span> </a> and <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> <span class="command"> <strong> ndbd </strong> </span> </a> servers explicitly. (Normally, these can be found in <code class="filename"> /usr/local/mysql/bin </code> .) </p> </div> <p> Finally, change location to the MySQL data directory (usually <code class="filename"> /var/lib/mysql </code> or <code class="filename"> /usr/local/mysql/data </code> ), and make sure that the <code class="filename"> my.cnf </code> file contains the option necessary to enable the NDB storage engine: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa43644783"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span> <span class="token constant">ndbcluster</span></code></pre> </div> <p> You can now start the MySQL server as usual: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa11789097"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysqld_safe</span> <span class="token constant">--user</span><span class="token attr-value"><span class="token punctuation">=</span>mysql</span> &</code></pre> </div> <p> Wait a moment to make sure the MySQL server is running properly. If you see the notice <code class="literal"> mysql ended </code> , check the server's <code class="filename"> .err </code> file to find out what went wrong. </p> <p> If all has gone well so far, you now can start using the cluster. Connect to the server and verify that the <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDBCLUSTER </code> </a> storage engine is enabled: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36151102"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">$<span class="token operator">></span> mysql Welcome <span class="token keyword">to</span> the MySQL monitor<span class="token punctuation">.</span> Commands <span class="token keyword">end</span> <span class="token keyword">with</span> <span class="token punctuation">;</span> <span class="token operator">or</span> \g<span class="token punctuation">.</span> Your MySQL <span class="token keyword">connection</span> id <span class="token operator">is</span> <span class="token number">1</span> <span class="token keyword">to</span> <span class="token keyword">server</span> version: <span class="token number">8.4</span><span class="token punctuation">.</span><span class="token number">3</span> <span class="token keyword">Type</span> <span class="token string">'help;'</span> <span class="token operator">or</span> <span class="token string">'\h'</span> <span class="token keyword">for</span> <span class="token keyword">help</span><span class="token punctuation">.</span> <span class="token keyword">Type</span> <span class="token string">'\c'</span> <span class="token keyword">to</span> clear the buffer<span class="token punctuation">.</span> <span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">ENGINES</span>\G <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 12. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Engine<span class="token punctuation">:</span> NDBCLUSTER Support<span class="token punctuation">:</span> YES Comment<span class="token punctuation">:</span> Clustered, fault-tolerant, memory-based tables <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 13. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Engine<span class="token punctuation">:</span> NDB Support<span class="token punctuation">:</span> YES Comment<span class="token punctuation">:</span> Alias for NDBCLUSTER ...</span></code></pre> </div> <p> The row numbers shown in the preceding example output may be different from those shown on your system, depending upon how your server is configured. </p> <p> Try to create an <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDBCLUSTER </code> </a> table: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16444736"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">$<span class="token operator">></span> mysql <span class="token prompt">mysql></span> <span class="token keyword">USE</span> test<span class="token punctuation">;</span> <span class="token keyword">Database</span> <span class="token keyword">changed</span> <span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> ctest <span class="token punctuation">(</span>i <span class="token datatype">INT</span><span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDBCLUSTER</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.09 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> ctest \G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> Table<span class="token punctuation">:</span> ctest Create Table<span class="token punctuation">:</span> CREATE TABLE `ctest` ( `i` int(11) default NULL ) ENGINE=ndbcluster DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci </span><span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> <p> To check that your nodes were set up properly, start the management client: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa11350256"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">ndb_mgm</span></code></pre> </div> <a class="indexterm" name="idm46045121953184"> </a> <p> Use the <span class="command"> <strong> SHOW </strong> </span> command from within the management client to obtain a report on the cluster's status: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ndbmgm"><div class="docs-select-all right" id="sa85074722"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ndbmgm"><span class="token prompt">ndb_mgm></span> <span class="token keyword">SHOW</span> Cluster Configuration <span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">--</span><span class="token operator">-</span> <span class="token selector">[ndbd(NDB)]</span> 1 node<span class="token punctuation">(</span>s<span class="token punctuation">)</span> id<span class="token operator">=</span>2 @127<span class="token punctuation">.</span>0<span class="token punctuation">.</span>0<span class="token punctuation">.</span>1 <span class="token punctuation">(</span>Version<span class="token operator">:</span> 8<span class="token punctuation">.</span>4<span class="token punctuation">.</span>0<span class="token operator">-</span>ndb<span class="token operator">-</span>8<span class="token punctuation">.</span>4<span class="token punctuation">.</span>0<span class="token punctuation">,</span> Nodegroup<span class="token operator">:</span> 0<span class="token punctuation">,</span> <span class="token operator">*</span><span class="token punctuation">)</span> <span class="token selector">[ndb_mgmd(MGM)]</span> 1 node<span class="token punctuation">(</span>s<span class="token punctuation">)</span> id<span class="token operator">=</span>1 @127<span class="token punctuation">.</span>0<span class="token punctuation">.</span>0<span class="token punctuation">.</span>1 <span class="token punctuation">(</span>Version<span class="token operator">:</span> 8<span class="token punctuation">.</span>4<span class="token punctuation">.</span>0<span class="token operator">-</span>ndb<span class="token operator">-</span>8<span class="token punctuation">.</span>4<span class="token punctuation">.</span>0<span class="token punctuation">)</span> <span class="token selector">[mysqld(API)]</span> 3 node<span class="token punctuation">(</span>s<span class="token punctuation">)</span> id<span class="token operator">=</span>3 @127<span class="token punctuation">.</span>0<span class="token punctuation">.</span>0<span class="token punctuation">.</span>1 <span class="token punctuation">(</span>Version<span class="token operator">:</span> 8<span class="token punctuation">.</span>4<span class="token punctuation">.</span>0<span class="token operator">-</span>ndb<span class="token operator">-</span>8<span class="token punctuation">.</span>4<span class="token punctuation">.</span>0<span class="token punctuation">)</span> id<span class="token operator">=</span>4 <span class="token punctuation">(</span>not connected<span class="token punctuation">,</span> accepting connect from any host<span class="token punctuation">)</span> id<span class="token operator">=</span>5 <span class="token punctuation">(</span>not connected<span class="token punctuation">,</span> accepting connect from any host<span class="token punctuation">)</span></code></pre> </div> <p> At this point, you have successfully set up a working NDB Cluster. You can now store data in the cluster by using any table created with <code class="literal"> ENGINE=NDBCLUSTER </code> or its alias <code class="literal"> ENGINE=NDB </code> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-tde-setup.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysql-cluster-tde-setup"> </a> 25.6.14.1 NDB File System Encryption Setup and Usage </h4> </div> </div> </div> <p> <span class="emphasis"> <em> Encryption of file system </em> </span> : To enable encryption of a previously unencrypted file system, the following steps are required: </p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p> Set the required data node parameters in the <code class="literal"> [ndbd default] </code> section of the <code class="filename"> config.ini </code> file, as shown here: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa24733928"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[ndbd default]</span> <span class="token constant">EncryptedFileSystem</span><span class="token attr-value"><span class="token punctuation">=</span> 1</span></code></pre> </div> <p> These parameters must be set as shown on all data nodes. </p> </li> <li class="listitem"> <p> Start the management server with either <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_initial"> <code class="option"> --initial </code> </a> or <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_reload"> <code class="option"> --reload </code> </a> to cause it to read the updated configuration file. </p> </li> <li class="listitem"> <p> Perform a rolling initial start (or restart) of all the data nodes (see <a class="xref" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster"> Section 25.6.5, “Performing a Rolling Restart of an NDB Cluster” </a> ): Start each data node with <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_initial"> <code class="option"> --initial </code> </a> ; in addition, supply either of the options <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_filesystem-password"> <code class="option"> --filesystem-password </code> </a> or <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_filesystem-password-from-stdin"> <code class="option"> --filesystem-password-from-stdin </code> </a> , plus a password, to each data node process. When you supply the password on the command line, a warning is shown, similar to this one: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa67561162"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">> ndbmtd <span class="token property">-c</span> 127<span class="token punctuation">.</span>0<span class="token punctuation">.</span>0<span class="token punctuation">.</span>1 <span class="token constant">--filesystem-password</span><span class="token attr-value"><span class="token punctuation">=</span>ndbsecret</span> ndbmtd<span class="token punctuation">:</span> <span class="token punctuation">[</span>Warning<span class="token punctuation">]</span> Using a password on the command line interface can be insecure<span class="token punctuation">.</span> 2022-08-22 16<span class="token punctuation">:</span>17<span class="token punctuation">:</span>58 <span class="token punctuation">[</span>ndbd<span class="token punctuation">]</span> INFO <span class="token property">--</span> Angel connected to <span class="token atrule">'127.0.0.1:1186'</span> 2022-08-22 16<span class="token punctuation">:</span>17<span class="token punctuation">:</span>58 <span class="token punctuation">[</span>ndbd<span class="token punctuation">]</span> INFO <span class="token property">--</span> Angel allocated nodeid<span class="token punctuation">:</span> 5</code></pre> </div> <p> <code class="option"> --filesystem-password </code> can accept the password form a file, <code class="literal"> tty </code> , or <code class="literal"> stdin </code> ; <code class="option"> --filesystem-password-from-stdin </code> accepts the password from <code class="literal"> stdin </code> only. The latter protects the password from exposure on the process command line or in the file system, and allows for the possibility of passing it from another secure application. </p> <p> You can also place the password in a <code class="filename"> my.cnf </code> file that can be read by the data node process, but not by other users of the system. Using the same password as in the previous example, the relevant portion of the file should look like this: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa11886616"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[ndbd]</span> <span class="token constant">filesystem-password</span><span class="token attr-value"><span class="token punctuation">=</span>ndbsecret</span></code></pre> </div> <p> You can also prompt the user starting the data node process to supply the encryption password when doing so, by using the <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_filesystem-password-from-stdin"> <code class="option"> --filesystem-password-from-stdin </code> </a> option in the <code class="filename"> my.cnf </code> file instead, like this: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa18566545"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[ndbd]</span> <span class="token constant">filesystem-password-from-stdin</span></code></pre> </div> <p> In this case, the user is prompted for the password when starting the data node process, as shown here: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ndbmgm"><div class="docs-select-all right" id="sa18121554"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ndbmgm"><span class="token operator">></span> ndbmtd <span class="token operator">-</span>c 127<span class="token punctuation">.</span>0<span class="token punctuation">.</span>0<span class="token punctuation">.</span>1 Enter filesystem password<span class="token operator">:</span> <span class="token operator"></span><span class="token operator"></span><span class="token operator"></span><span class="token operator"></span><span class="token operator">*</span> <span class="token selector">2022-08-22 16:36:00 [ndbd]</span> <span class="token datatype">INFO</span> <span class="token operator">--</span> Angel connected to '127<span class="token punctuation">.</span>0<span class="token punctuation">.</span>0<span class="token punctuation">.</span>1<span class="token operator">:</span>1186' <span class="token selector">2022-08-22 16:36:00 [ndbd]</span> <span class="token datatype">INFO</span> <span class="token operator">--</span> Angel allocated nodeid<span class="token operator">:</span> 5 <span class="token operator">></span></code></pre> </div> <p> Regardless of the method used, the format of the encryption password is the same as that used for passwords for encrypted backups (see <a class="xref" href="mysql-cluster-backup-using-management-client.html" title="25.6.8.2 Using The NDB Cluster Management Client to Create a Backup"> Section 25.6.8.2, “Using The NDB Cluster Management Client to Create a Backup” </a> ); the password must be supplied when starting each data node process; otherwise the data node process cannot start. This is indicated by the following message in the data node log: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa57750876"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">> tail <span class="token property">-n2</span> ndb_5_out<span class="token punctuation">.</span>log 2022-08-22 16<span class="token punctuation">:</span>08<span class="token punctuation">:</span>30 <span class="token punctuation">[</span>ndbd<span class="token punctuation">]</span> INFO <span class="token property">--</span> Data node configured to have encryption but password not provided 2022-08-22 16<span class="token punctuation">:</span>08<span class="token punctuation">:</span>31 <span class="token punctuation">[</span>ndbd<span class="token punctuation">]</span> ALERT <span class="token property">--</span> Node 5<span class="token punctuation">:</span> Forced node shutdown completed<span class="token punctuation">.</span> Occurred during startphase 0<span class="token punctuation">.</span></code></pre> </div> <p> When restarted as just described, each data node clears its on-disk state, and rebuilds it in encrypted form. </p> </li> </ol> </div> <p> <span class="emphasis"> <em> Rotation of File system password </em> </span> : To update the encryption password used by the data nodes, perform a rolling initial restart of the data nodes, supplying the new password to each data node when restarting it using <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_filesystem-password"> <code class="option"> --filesystem-password </code> </a> or <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_filesystem-password-from-stdin"> <code class="option"> --filesystem-password-from-stdin </code> </a> . </p> <p> <span class="emphasis"> <em> Decryption of file system </em> </span> : To remove encryption from an encrypted file system, do the following: </p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p> In the <code class="literal"> [ndbd default] </code> section of the <code class="filename"> config.ini </code> file, set <code class="literal"> EncryptedFileSystem = OFF </code> . </p> </li> <li class="listitem"> <p> Restart the management server with <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_initial"> <code class="option"> --initial </code> </a> or <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_reload"> <code class="option"> --reload </code> </a> . </p> </li> <li class="listitem"> <p> Perform a rolling initial restart of the data nodes. Do <span class="emphasis"> <em> not </em> </span> use any password-related options when restarting the node binaries. </p> <p> When restarted, each data node clears its on-disk state, and rebuilds it in unencrypted form. </p> </li> </ol> </div> <p> To see whether file system encryption is properly configured, you can use a query against the <code class="literal"> ndbinfo </code> <a class="link" href="mysql-cluster-ndbinfo-config-values.html" title="25.6.17.12 The ndbinfo config_values Table"> <code class="literal"> config_values </code> </a> and <a class="link" href="mysql-cluster-ndbinfo-config-params.html" title="25.6.17.11 The ndbinfo config_params Table"> <code class="literal"> config_params </code> </a> tables similar to this one: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30908465"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> v<span class="token punctuation">.</span>node_id <span class="token keyword">AS</span> Node<span class="token punctuation">,</span> p<span class="token punctuation">.</span>param_name <span class="token keyword">AS</span> Parameter<span class="token punctuation">,</span> v<span class="token punctuation">.</span>config_value <span class="token keyword">AS</span> <span class="token keyword">Value</span> <span class="token prompt"> -></span> <span class="token keyword">FROM</span> ndbinfo<span class="token punctuation">.</span>config_values v <span class="token prompt"> -></span> <span class="token keyword">JOIN</span> ndbinfo<span class="token punctuation">.</span>config_params p <span class="token prompt"> -></span> <span class="token keyword">ON</span> v<span class="token punctuation">.</span>config_param<span class="token operator">=</span>p<span class="token punctuation">.</span>param_number <span class="token prompt"> -></span> <span class="token keyword">WHERE</span> p<span class="token punctuation">.</span>param_name<span class="token operator">=</span><span class="token string">'EncryptedFileSystem'</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> Node <span class="token punctuation">\|</span> Parameter <span class="token punctuation">\|</span> Value <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 5 <span class="token punctuation">\|</span> EncryptedFileSystem <span class="token punctuation">\|</span> 1 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> 6 <span class="token punctuation">\|</span> EncryptedFileSystem <span class="token punctuation">\|</span> 1 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> 7 <span class="token punctuation">\|</span> EncryptedFileSystem <span class="token punctuation">\|</span> 1 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> 8 <span class="token punctuation">\|</span> EncryptedFileSystem <span class="token punctuation">\|</span> 1 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">4 rows in set (0.10 sec)</span></code></pre> </div> <p> Here, <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-encryptedfilesystem"> <code class="literal"> EncryptedFileSystem </code> </a> is equal to <code class="literal"> 1 </code> on all data nodes, which means that filesystem encryption is enabled for this cluster. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/sys-ps-is-account-enabled.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="sys-ps-is-account-enabled"> </a> 30.4.5.9 The ps_is_account_enabled() Function </h4> </div> </div> </div> <a class="indexterm" name="idm46045060891392"> </a> <a class="indexterm" name="idm46045060889888"> </a> <p> Returns <code class="literal"> YES </code> or <code class="literal"> NO </code> to indicate whether Performance Schema instrumentation for a given account is enabled. </p> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="sys-ps-is-account-enabled-parameters"> </a> Parameters </h5> </div> </div> </div> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> in_host VARCHAR(60) </code> : The host name of the account to check. </p> </li> <li class="listitem"> <p> <code class="literal"> in_user VARCHAR(32) </code> : The user name of the account to check. </p> </li> </ul> </div> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="sys-ps-is-account-enabled-return-value"> </a> Return Value </h5> </div> </div> </div> <p> An <code class="literal"> ENUM('YES','NO') </code> value. </p> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="sys-ps-is-account-enabled-example"> </a> Example </h5> </div> </div> </div> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa92271033"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> sys<span class="token punctuation">.</span>ps_is_account_enabled<span class="token punctuation">(</span><span class="token string">'localhost'</span><span class="token punctuation">,</span> <span class="token string">'root'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> sys.ps_is_account_enabled('localhost', 'root') <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> YES <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/source-installation.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="source-installation"> </a> 2.8 Installing MySQL from Source </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <span class="section"> <a href="source-installation-methods.html"> 2.8.1 Source Installation Methods </a> </span> </dt> <dt> <span class="section"> <a href="source-installation-prerequisites.html"> 2.8.2 Source Installation Prerequisites </a> </span> </dt> <dt> <span class="section"> <a href="source-installation-layout.html"> 2.8.3 MySQL Layout for Source Installation </a> </span> </dt> <dt> <span class="section"> <a href="installing-source-distribution.html"> 2.8.4 Installing MySQL Using a Standard Source Distribution </a> </span> </dt> <dt> <span class="section"> <a href="installing-development-tree.html"> 2.8.5 Installing MySQL Using a Development Source Tree </a> </span> </dt> <dt> <span class="section"> <a href="source-ssl-library-configuration.html"> 2.8.6 Configuring SSL Library Support </a> </span> </dt> <dt> <span class="section"> <a href="source-configuration-options.html"> 2.8.7 MySQL Source-Configuration Options </a> </span> </dt> <dt> <span class="section"> <a href="compilation-problems.html"> 2.8.8 Dealing with Problems Compiling MySQL </a> </span> </dt> <dt> <span class="section"> <a href="source-configuration-third-party.html"> 2.8.9 MySQL Configuration and Third-Party Tools </a> </span> </dt> <dt> <span class="section"> <a href="source-installation-doxygen.html"> 2.8.10 Generating MySQL Doxygen Documentation Content </a> </span> </dt> </dl> </div> <a class="indexterm" name="idm46045329722592"> </a> <a class="indexterm" name="idm46045329721136"> </a> <a class="indexterm" name="idm46045329719648"> </a> <p> Building MySQL from the source code enables you to customize build parameters, compiler optimizations, and installation location. For a list of systems on which MySQL is known to run, see <a class="ulink" href="https://www.mysql.com/support/supportedplatforms/database.html" target="_blank"> https://www.mysql.com/support/supportedplatforms/database.html </a> . </p> <p> Before you proceed with an installation from source, check whether Oracle produces a precompiled binary distribution for your platform and whether it works for you. We put a great deal of effort into ensuring that our binaries are built with the best possible options for optimal performance. Instructions for installing binary distributions are available in <a class="xref" href="binary-installation.html" title="2.2 Installing MySQL on Unix/Linux Using Generic Binaries"> Section 2.2, “Installing MySQL on Unix/Linux Using Generic Binaries” </a> . </p> <a class="indexterm" name="idm46045329715904"> </a> <p> If you are interested in building MySQL from a source distribution using build options the same as or similar to those use by Oracle to produce binary distributions on your platform, obtain a binary distribution, unpack it, and look in the <code class="filename"> docs/INFO_BIN </code> file, which contains information about how that MySQL distribution was configured and compiled. </p> <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Warning </div> <p> Building MySQL with nonstandard options may lead to reduced functionality, performance, or security. </p> </div> <p> The MySQL source code contains internal documentation written using Doxygen. The generated Doxygen content is available at <a class="ulink" href="/doc/index-other.html" target="_top"> https://dev.mysql.com/doc/index-other.html </a> . It is also possible to generate this content locally from a MySQL source distribution using the instructions at <a class="xref" href="source-installation-doxygen.html" title="2.8.10 Generating MySQL Doxygen Documentation Content"> Section 2.8.10, “Generating MySQL Doxygen Documentation Content” </a> . </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-processes.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysql-cluster-ndbinfo-processes"> </a> 25.6.17.51 The ndbinfo processes Table </h4> </div> </div> </div> <a class="indexterm" name="idm46045088252656"> </a> <p> This table contains information about NDB Cluster node processes; each node is represented by the row in the table. Only nodes that are connected to the cluster are shown in this table. You can obtain information about nodes that are configured but not connected to the cluster from the <a class="link" href="mysql-cluster-ndbinfo-nodes.html" title="25.6.17.48 The ndbinfo nodes Table"> <code class="literal"> nodes </code> </a> and <a class="link" href="mysql-cluster-ndbinfo-config-nodes.html" title="25.6.17.10 The ndbinfo config_nodes Table"> <code class="literal"> config_nodes </code> </a> tables. </p> <p> The <code class="literal"> processes </code> table contains the following columns: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> node_id </code> </p> <p> The node's unique node ID in the cluster </p> </li> <li class="listitem"> <p> <code class="literal"> node_type </code> </p> <p> Type of node (management, data, or API node; see text) </p> </li> <li class="listitem"> <p> <code class="literal"> node_version </code> </p> <p> Version of the <code class="literal"> NDB </code> software program running on this node. </p> </li> <li class="listitem"> <p> <code class="literal"> process_id </code> </p> <p> This node's process ID </p> </li> <li class="listitem"> <p> <code class="literal"> angel_process_id </code> </p> <p> Process ID of this node's angel process </p> </li> <li class="listitem"> <p> <code class="literal"> process_name </code> </p> <p> Name of the executable </p> </li> <li class="listitem"> <p> <code class="literal"> service_URI </code> </p> <p> Service URI of this node (see text) </p> </li> </ul> </div> <h5> <a name="idm46045088232096"> </a> Notes </h5> <p> <code class="literal"> node_id </code> is the ID assigned to this node in the cluster. </p> <p> The <code class="literal"> node_type </code> column displays one of the following three values: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> MGM </code> : Management node. </p> </li> <li class="listitem"> <p> <code class="literal"> NDB </code> : Data node. </p> </li> <li class="listitem"> <p> <code class="literal"> API </code> : API or SQL node. </p> </li> </ul> </div> <p> For an executable shipped with the NDB Cluster distribution, <code class="literal"> node_version </code> shows the software Cluster version string, such as <code class="literal"> 8.4.0-ndb-8.4.0 </code> . </p> <p> <code class="literal"> process_id </code> is the node executable's process ID as shown by the host operating system using a process display application such as <span class="command"> <strong> top </strong> </span> on Linux, or the Task Manager on Windows platforms. </p> <p> <code class="literal"> angel_process_id </code> is the system process ID for the node's angel process, which ensures that a data node or SQL is automatically restarted in cases of failures. For management nodes and API nodes other than SQL nodes, the value of this column is <code class="literal"> NULL </code> . </p> <p> The <code class="literal"> process_name </code> column shows the name of the running executable. For management nodes, this is <code class="literal"> ndb_mgmd </code> . For data nodes, this is <code class="literal"> ndbd </code> (single-threaded) or <code class="literal"> ndbmtd </code> (multithreaded). For SQL nodes, this is <code class="literal"> mysqld </code> . For other types of API nodes, it is the name of the executable program connected to the cluster; NDB API applications can set a custom value for this using <a class="ulink" href="/doc/ndbapi/en/ndb-ndb-cluster-connection.html#ndb-ndb-cluster-connection-set-name" target="_top"> <code class="literal"> Ndb_cluster_connection::set_name() </code> </a> . </p> <p> <code class="literal"> service_URI </code> shows the service network address. For management nodes and data nodes, the scheme used is <code class="literal"> ndb:// </code> . For SQL nodes, this is <code class="literal"> mysql:// </code> . By default, API nodes other than SQL nodes use <code class="literal"> ndb:// </code> for the scheme; NDB API applications can set this to a custom value using <code class="literal"> Ndb_cluster_connection::set_service_uri() </code> . regardless of the node type, the scheme is followed by the IP address used by the NDB transporter for the node in question. For management nodes and SQL nodes, this address includes the port number (usually 1186 for management nodes and 3306 for SQL nodes). If the SQL node was started with the <a class="link" href="server-system-variables.html#sysvar_bind_address"> <code class="literal"> bind_address </code> </a> system variable set, this address is used instead of the transporter address, unless the bind address is set to <code class="literal"> * </code> , <code class="literal"> 0.0.0.0 </code> , or <code class="literal"> :: </code> . </p> <p> Additional path information may be included in the <code class="literal"> service_URI </code> value for an SQL node reflecting various configuration options. For example, <code class="literal"> mysql://198.51.100.3/tmp/mysql.sock </code> indicates that the SQL node was started with the <a class="link" href="server-system-variables.html#sysvar_skip_networking"> <code class="literal"> skip_networking </code> </a> system variable enabled, and <code class="literal"> mysql://198.51.100.3:3306/?server-id=1 </code> shows that replication is enabled for this SQL node. </p> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/json-utility-functions.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="json-utility-functions"> </a> 14.17.8 JSON Utility Functions </h3> </div> </div> </div> <p> This section documents utility functions that act on JSON values, or strings that can be parsed as JSON values. <a class="link" href="json-utility-functions.html#function_json-pretty"> <code class="literal"> JSON_PRETTY() </code> </a> prints out a JSON value in a format that is easy to read. <a class="link" href="json-utility-functions.html#function_json-storage-size"> <code class="literal"> JSON_STORAGE_SIZE() </code> </a> and <a class="link" href="json-utility-functions.html#function_json-storage-free"> <code class="literal"> JSON_STORAGE_FREE() </code> </a> show, respectively, the amount of storage space used by a given JSON value and the amount of space remaining in a <code class="literal"> JSON </code> column following a partial update. </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <a name="function_json-pretty"> </a> <p> <a class="link" href="json-utility-functions.html#function_json-pretty"> <code class="literal"> JSON_PRETTY( <em class="replaceable"> <code> json_val </code> </em> ) </code> </a> </p> <a class="indexterm" name="idm46045194253936"> </a> <p> Provides pretty-printing of JSON values similar to that implemented in PHP and by other languages and database systems. The value supplied must be a JSON value or a valid string representation of a JSON value. Extraneous whitespaces and newlines present in this value have no effect on the output. For a <code class="literal"> NULL </code> value, the function returns <code class="literal"> NULL </code> . If the value is not a JSON document, or if it cannot be parsed as one, the function fails with an error. </p> <p> Formatting of the output from this function adheres to the following rules: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> Each array element or object member appears on a separate line, indented by one additional level as compared to its parent. </p> </li> <li class="listitem"> <p> Each level of indentation adds two leading spaces. </p> </li> <li class="listitem"> <p> A comma separating individual array elements or object members is printed before the newline that separates the two elements or members. </p> </li> <li class="listitem"> <p> The key and the value of an object member are separated by a colon followed by a space (' <code class="literal"> : </code> '). </p> </li> <li class="listitem"> <p> An empty object or array is printed on a single line. No space is printed between the opening and closing brace. </p> </li> <li class="listitem"> <p> Special characters in string scalars and key names are escaped employing the same rules used by the <a class="link" href="json-creation-functions.html#function_json-quote"> <code class="literal"> JSON_QUOTE() </code> </a> function. </p> </li> </ul> </div> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa27010127"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">JSON_PRETTY</span><span class="token punctuation">(</span><span class="token string">'123'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true"># scalar</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> JSON_PRETTY('123') <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 123 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">JSON_PRETTY</span><span class="token punctuation">(</span><span class="token string">"[1,3,5]"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true"># array</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> JSON_PRETTY("[1,3,5]") <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token operator">\|</span> <span class="token punctuation">[</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">5</span> <span class="token punctuation">]</span> <span class="token operator">\|</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">JSON_PRETTY</span><span class="token punctuation">(</span><span class="token string">'{"a":"10","b":"15","x":"25"}'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment" spellcheck="true"># object</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> JSON_PRETTY('{"a":"10","b":"15","x":"25"}') <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token operator">\|</span> { <span class="token string">"a"</span>: <span class="token string">"10"</span><span class="token punctuation">,</span> <span class="token string">"b"</span>: <span class="token string">"15"</span><span class="token punctuation">,</span> <span class="token string">"x"</span>: <span class="token string">"25"</span> } <span class="token operator">\|</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">JSON_PRETTY</span><span class="token punctuation">(</span><span class="token string">'["a",1,{"key1": '</span><span class="token operator">></span> <span class="token string">"value1"</span>}<span class="token punctuation">,</span><span class="token string">"5"</span><span class="token punctuation">,</span> <span class="token string">"77"</span> <span class="token punctuation">,</span> <span class="token string">'> {"key2":["value3","valueX", '</span><span class="token operator">></span> <span class="token string">"valueY"</span><span class="token punctuation">]</span>}<span class="token punctuation">,</span><span class="token string">"j"</span><span class="token punctuation">,</span> <span class="token string">"2"</span> <span class="token punctuation">]</span><span class="token string">')\G # nested arrays and objects ************************* 1. row ************************* JSON_PRETTY('</span><span class="token inlinejson"><span class="token punctuation">[</span><span class="token string">"a"</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token punctuation">{</span><span class="token property">"key1"</span><span class="token operator">:</span> <span class="token string">"value1"</span><span class="token punctuation">}</span><span class="token punctuation">,</span><span class="token string">"5"</span><span class="token punctuation">,</span> <span class="token string">"77"</span> <span class="token punctuation">,</span> <span class="token punctuation">{</span><span class="token property">"key2"</span><span class="token operator">:</span><span class="token punctuation">[</span><span class="token string">"value3"</span><span class="token punctuation">,</span><span class="token string">"valuex"</span><span class="token punctuation">,</span> <span class="token string">"valuey"</span><span class="token punctuation">]</span><span class="token punctuation">}</span><span class="token punctuation">,</span><span class="token string">"j"</span><span class="token punctuation">,</span> <span class="token string">"2"</span> <span class="token punctuation">]</span>'<span class="token punctuation">)</span><span class="token operator">:</span> <span class="token punctuation">[</span> <span class="token string">"a"</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token punctuation">{</span> <span class="token property">"key1"</span><span class="token operator">:</span> <span class="token string">"value1"</span> <span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token string">"5"</span><span class="token punctuation">,</span> <span class="token string">"77"</span><span class="token punctuation">,</span> <span class="token punctuation">{</span> <span class="token property">"key2"</span><span class="token operator">:</span> <span class="token punctuation">[</span> <span class="token string">"value3"</span><span class="token punctuation">,</span> <span class="token string">"valuex"</span><span class="token punctuation">,</span> <span class="token string">"valuey"</span> <span class="token punctuation">]</span> <span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token string">"j"</span><span class="token punctuation">,</span> <span class="token string">"2"</span> <span class="token punctuation">]</span></span></code></pre> </div> </li> <li class="listitem"> <a name="function_json-storage-free"> </a> <p> <a class="link" href="json-utility-functions.html#function_json-storage-free"> <code class="literal"> JSON_STORAGE_FREE( <em class="replaceable"> <code> json_val </code> </em> ) </code> </a> </p> <a class="indexterm" name="idm46045194228128"> </a> <p> For a <a class="link" href="json.html" title="13.5 The JSON Data Type"> <code class="literal"> JSON </code> </a> column value, this function shows how much storage space was freed in its binary representation after it was updated in place using <a class="link" href="json-modification-functions.html#function_json-set"> <code class="literal"> JSON_SET() </code> </a> , <a class="link" href="json-modification-functions.html#function_json-replace"> <code class="literal"> JSON_REPLACE() </code> </a> , or <a class="link" href="json-modification-functions.html#function_json-remove"> <code class="literal"> JSON_REMOVE() </code> </a> . The argument can also be a valid JSON document or a string which can be parsed as one—either as a literal value or as the value of a user variable—in which case the function returns 0. It returns a positive, nonzero value if the argument is a <code class="literal"> JSON </code> column value which has been updated as described previously, such that its binary representation takes up less space than it did prior to the update. For a <code class="literal"> JSON </code> column which has been updated such that its binary representation is the same as or larger than before, or if the update was not able to take advantage of a partial update, it returns 0; it returns <code class="literal"> NULL </code> if the argument is <code class="literal"> NULL </code> . </p> <p> If <em class="replaceable"> <code> json_val </code> </em> is not <code class="literal"> NULL </code> , and neither is a valid JSON document nor can be successfully parsed as one, an error results. </p> <p> In this example, we create a table containing a <code class="literal"> JSON </code> column, then insert a row containing a JSON object: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa52974016"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> jtable <span class="token punctuation">(</span>jcol <span class="token datatype">JSON</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.38 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> jtable <span class="token keyword">VALUES</span> <span class="token prompt"> -></span> <span class="token punctuation">(</span><span class="token string">'{"a": 10, "b": "wxyz", "c": "[true, false]"}'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 1 row affected (0.04 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> jtable<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> jcol <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> {"a": 10, "b": "wxyz", "c": "[true, false]"} <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> <p> Now we update the column value using <code class="literal"> JSON_SET() </code> such that a partial update can be performed; in this case, we replace the value pointed to by the <code class="literal"> c </code> key (the array <code class="literal"> [true, false] </code> ) with one that takes up less space (the integer <code class="literal"> 1 </code> ): </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa80443634"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">UPDATE</span> jtable <span class="token prompt"> -></span> <span class="token keyword">SET</span> jcol <span class="token operator">=</span> <span class="token function">JSON_SET</span><span class="token punctuation">(</span>jcol<span class="token punctuation">,</span> <span class="token string">"$.a"</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">,</span> <span class="token string">"$.b"</span><span class="token punctuation">,</span> <span class="token string">"wxyz"</span><span class="token punctuation">,</span> <span class="token string">"$.c"</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 1 row affected (0.03 sec)</span> <span class="token output">Rows matched: 1 Changed: 1 Warnings: 0</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> jtable<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> jcol <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> {"a": 10, "b": "wxyz", "c": 1} <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">JSON_STORAGE_FREE</span><span class="token punctuation">(</span>jcol<span class="token punctuation">)</span> <span class="token keyword">FROM</span> jtable<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> JSON_STORAGE_FREE(jcol) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 14 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> <p> The effects of successive partial updates on this free space are cumulative, as shown in this example using <code class="literal"> JSON_SET() </code> to reduce the space taken up by the value having key <code class="literal"> b </code> (and making no other changes): </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa4410044"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">UPDATE</span> jtable <span class="token prompt"> -></span> <span class="token keyword">SET</span> jcol <span class="token operator">=</span> <span class="token function">JSON_SET</span><span class="token punctuation">(</span>jcol<span class="token punctuation">,</span> <span class="token string">"$.a"</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">,</span> <span class="token string">"$.b"</span><span class="token punctuation">,</span> <span class="token string">"wx"</span><span class="token punctuation">,</span> <span class="token string">"$.c"</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 1 row affected (0.03 sec)</span> <span class="token output">Rows matched: 1 Changed: 1 Warnings: 0</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">JSON_STORAGE_FREE</span><span class="token punctuation">(</span>jcol<span class="token punctuation">)</span> <span class="token keyword">FROM</span> jtable<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> JSON_STORAGE_FREE(jcol) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 16 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> <p> Updating the column without using <code class="literal"> JSON_SET() </code> , <code class="literal"> JSON_REPLACE() </code> , or <code class="literal"> JSON_REMOVE() </code> means that the optimizer cannot perform the update in place; in this case, <code class="literal"> JSON_STORAGE_FREE() </code> returns 0, as shown here: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa95017245"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">UPDATE</span> jtable <span class="token keyword">SET</span> jcol <span class="token operator">=</span> <span class="token string">'{"a": 10, "b": 1}'</span><span class="token punctuation">;</span> <span class="token output">Query OK, 1 row affected (0.05 sec)</span> <span class="token output">Rows matched: 1 Changed: 1 Warnings: 0</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">JSON_STORAGE_FREE</span><span class="token punctuation">(</span>jcol<span class="token punctuation">)</span> <span class="token keyword">FROM</span> jtable<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> JSON_STORAGE_FREE(jcol) <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 0 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> <p> Partial updates of JSON documents can be performed only on column values. For a user variable that stores a JSON value, the value is always completely replaced, even when the update is performed using <code class="literal"> JSON_SET() </code> : </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa93070926"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@j</span> <span class="token operator">=</span> <span class="token string">'{"a": 10, "b": "wxyz", "c": "[true, false]"}'</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@j</span> <span class="token operator">=</span> <span class="token function">JSON_SET</span><span class="token punctuation">(</span><span class="token variable">@j</span><span class="token punctuation">,</span> <span class="token string">'$.a'</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">,</span> <span class="token string">'$.b'</span><span class="token punctuation">,</span> <span class="token string">'wxyz'</span><span class="token punctuation">,</span> <span class="token string">'$.c'</span><span class="token punctuation">,</span> <span class="token string">'1'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@j</span><span class="token punctuation">,</span> <span class="token function">JSON_STORAGE_FREE</span><span class="token punctuation">(</span><span class="token variable">@j</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> Free<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> @j <span class="token punctuation">\|</span> Free <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> {"a": 10, "b": "wxyz", "c": "1"} <span class="token punctuation">\|</span> 0 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> <p> For a JSON literal, this function always returns 0: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa94593370"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">JSON_STORAGE_FREE</span><span class="token punctuation">(</span><span class="token string">'{"a": 10, "b": "wxyz", "c": "1"}'</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> Free<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> Free <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 0 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> </li> <li class="listitem"> <a name="function_json-storage-size"> </a> <p> <a class="link" href="json-utility-functions.html#function_json-storage-size"> <code class="literal"> JSON_STORAGE_SIZE( <em class="replaceable"> <code> json_val </code> </em> ) </code> </a> </p> <a class="indexterm" name="idm46045194177200"> </a> <p> This function returns the number of bytes used to store the binary representation of a JSON document. When the argument is a <code class="literal"> JSON </code> column, this is the space used to store the JSON document as it was inserted into the column, prior to any partial updates that may have been performed on it afterwards. <em class="replaceable"> <code> json_val </code> </em> must be a valid JSON document or a string which can be parsed as one. In the case where it is string, the function returns the amount of storage space in the JSON binary representation that is created by parsing the string as JSON and converting it to binary. It returns <code class="literal"> NULL </code> if the argument is <code class="literal"> NULL </code> . </p> <p> An error results when <em class="replaceable"> <code> json_val </code> </em> is not <code class="literal"> NULL </code> , and is not—or cannot be successfully parsed as—a JSON document. </p> <p> To illustrate this function's behavior when used with a <code class="literal"> JSON </code> column as its argument, we create a table named <code class="literal"> jtable </code> containing a <code class="literal"> JSON </code> column <code class="literal"> jcol </code> , insert a JSON value into the table, then obtain the storage space used by this column with <code class="literal"> JSON_STORAGE_SIZE() </code> , as shown here: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa24605229"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> jtable <span class="token punctuation">(</span>jcol <span class="token datatype">JSON</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.42 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> jtable <span class="token keyword">VALUES</span> <span class="token prompt"> -></span> <span class="token punctuation">(</span><span class="token string">'{"a": 1000, "b": "wxyz", "c": "[1, 3, 5, 7]"}'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 1 row affected (0.04 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token prompt"> -></span> jcol<span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token function">JSON_STORAGE_SIZE</span><span class="token punctuation">(</span>jcol<span class="token punctuation">)</span> <span class="token keyword">AS</span> Size<span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token function">JSON_STORAGE_FREE</span><span class="token punctuation">(</span>jcol<span class="token punctuation">)</span> <span class="token keyword">AS</span> Free <span class="token prompt"> -></span> <span class="token keyword">FROM</span> jtable<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> jcol <span class="token punctuation">\|</span> Size <span class="token punctuation">\|</span> Free <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> {"a": 1000, "b": "wxyz", "c": "[1, 3, 5, 7]"} <span class="token punctuation">\|</span> 47 <span class="token punctuation">\|</span> 0 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> <p> According to the output of <code class="literal"> JSON_STORAGE_SIZE() </code> , the JSON document inserted into the column takes up 47 bytes. We also checked the amount of space freed by any previous partial updates of the column using <a class="link" href="json-utility-functions.html#function_json-storage-free"> <code class="literal"> JSON_STORAGE_FREE() </code> </a> ; since no updates have yet been performed, this is 0, as expected. </p> <p> Next we perform an <a class="link" href="update.html" title="15.2.17 UPDATE Statement"> <code class="literal"> UPDATE </code> </a> on the table that should result in a partial update of the document stored in <code class="literal"> jcol </code> , and then test the result as shown here: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa22006261"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">UPDATE</span> jtable <span class="token keyword">SET</span> jcol <span class="token operator">=</span> <span class="token prompt"> -></span> <span class="token function">JSON_SET</span><span class="token punctuation">(</span>jcol<span class="token punctuation">,</span> <span class="token string">"$.b"</span><span class="token punctuation">,</span> <span class="token string">"a"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 1 row affected (0.04 sec)</span> <span class="token output">Rows matched: 1 Changed: 1 Warnings: 0</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token prompt"> -></span> jcol<span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token function">JSON_STORAGE_SIZE</span><span class="token punctuation">(</span>jcol<span class="token punctuation">)</span> <span class="token keyword">AS</span> Size<span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token function">JSON_STORAGE_FREE</span><span class="token punctuation">(</span>jcol<span class="token punctuation">)</span> <span class="token keyword">AS</span> Free <span class="token prompt"> -></span> <span class="token keyword">FROM</span> jtable<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> jcol <span class="token punctuation">\|</span> Size <span class="token punctuation">\|</span> Free <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> {"a": 1000, "b": "a", "c": "[1, 3, 5, 7]"} <span class="token punctuation">\|</span> 47 <span class="token punctuation">\|</span> 3 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> <p> The value returned by <code class="literal"> JSON_STORAGE_FREE() </code> in the previous query indicates that a partial update of the JSON document was performed, and that this freed 3 bytes of space used to store it. The result returned by <code class="literal"> JSON_STORAGE_SIZE() </code> is unchanged by the partial update. </p> <p> Partial updates are supported for updates using <a class="link" href="json-modification-functions.html#function_json-set"> <code class="literal"> JSON_SET() </code> </a> , <a class="link" href="json-modification-functions.html#function_json-replace"> <code class="literal"> JSON_REPLACE() </code> </a> , or <a class="link" href="json-modification-functions.html#function_json-remove"> <code class="literal"> JSON_REMOVE() </code> </a> . The direct assignment of a value to a <code class="literal"> JSON </code> column cannot be partially updated; following such an update, <code class="literal"> JSON_STORAGE_SIZE() </code> always shows the storage used for the newly-set value: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa1693583"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">UPDATE</span> jtable <span class="token prompt">mysql></span> <span class="token keyword">SET</span> jcol <span class="token operator">=</span> <span class="token string">'{"a": 4.55, "b": "wxyz", "c": "[true, false]"}'</span><span class="token punctuation">;</span> <span class="token output">Query OK, 1 row affected (0.04 sec)</span> <span class="token output">Rows matched: 1 Changed: 1 Warnings: 0</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token prompt"> -></span> jcol<span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token function">JSON_STORAGE_SIZE</span><span class="token punctuation">(</span>jcol<span class="token punctuation">)</span> <span class="token keyword">AS</span> Size<span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token function">JSON_STORAGE_FREE</span><span class="token punctuation">(</span>jcol<span class="token punctuation">)</span> <span class="token keyword">AS</span> Free <span class="token prompt"> -></span> <span class="token keyword">FROM</span> jtable<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> jcol <span class="token punctuation">\|</span> Size <span class="token punctuation">\|</span> Free <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> {"a": 4.55, "b": "wxyz", "c": "[true, false]"} <span class="token punctuation">\|</span> 56 <span class="token punctuation">\|</span> 0 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> <p> A JSON user variable cannot be partially updated. This means that this function always shows the space currently used to store a JSON document in a user variable: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa72757799"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@j</span> <span class="token operator">=</span> <span class="token string">'[100, "sakila", [1, 3, 5], 425.05]'</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@j</span><span class="token punctuation">,</span> <span class="token function">JSON_STORAGE_SIZE</span><span class="token punctuation">(</span><span class="token variable">@j</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> Size<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> @j <span class="token punctuation">\|</span> Size <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> [100, "sakila", [1, 3, 5], 425.05] <span class="token punctuation">\|</span> 45 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@j</span> <span class="token operator">=</span> <span class="token function">JSON_SET</span><span class="token punctuation">(</span><span class="token variable">@j</span><span class="token punctuation">,</span> <span class="token string">'$[1]'</span><span class="token punctuation">,</span> <span class="token string">"json"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@j</span><span class="token punctuation">,</span> <span class="token function">JSON_STORAGE_SIZE</span><span class="token punctuation">(</span><span class="token variable">@j</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> Size<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> @j <span class="token punctuation">\|</span> Size <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> [100, "json", [1, 3, 5], 425.05] <span class="token punctuation">\|</span> 43 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@j</span> <span class="token operator">=</span> <span class="token function">JSON_SET</span><span class="token punctuation">(</span><span class="token variable">@j</span><span class="token punctuation">,</span> <span class="token string">'$[2][0]'</span><span class="token punctuation">,</span> <span class="token function">JSON_ARRAY</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">,</span> <span class="token number">20</span><span class="token punctuation">,</span> <span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token variable">@j</span><span class="token punctuation">,</span> <span class="token function">JSON_STORAGE_SIZE</span><span class="token punctuation">(</span><span class="token variable">@j</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> Size<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> @j <span class="token punctuation">\|</span> Size <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> [100, "json", [[10, 20, 30], 3, 5], 425.05] <span class="token punctuation">\|</span> 56 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> <p> For a JSON literal, this function always returns the current storage space used: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99951128"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token prompt"> -></span> <span class="token function">JSON_STORAGE_SIZE</span><span class="token punctuation">(</span><span class="token string">'[100, "sakila", [1, 3, 5], 425.05]'</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> A<span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token function">JSON_STORAGE_SIZE</span><span class="token punctuation">(</span><span class="token string">'{"a": 1000, "b": "a", "c": "[1, 3, 5, 7]"}'</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> B<span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token function">JSON_STORAGE_SIZE</span><span class="token punctuation">(</span><span class="token string">'{"a": 1000, "b": "wxyz", "c": "[1, 3, 5, 7]"}'</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> C<span class="token punctuation">,</span> <span class="token prompt"> -></span> <span class="token function">JSON_STORAGE_SIZE</span><span class="token punctuation">(</span><span class="token string">'[100, "json", [[10, 20, 30], 3, 5], 425.05]'</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> D<span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> A <span class="token punctuation">\|</span> B <span class="token punctuation">\|</span> C <span class="token punctuation">\|</span> D <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> 45 <span class="token punctuation">\|</span> 44 <span class="token punctuation">\|</span> 47 <span class="token punctuation">\|</span> 56 <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">1 row in set (0.00 sec)</span></code></pre> </div> </li> </ul> </div> </div> <br/> </div>
https://dev.mysql.com/doc/refman/8.4/en/innodb-information-schema-metrics-table.html	<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="innodb-information-schema-metrics-table"> </a> 17.15.6 InnoDB INFORMATION_SCHEMA Metrics Table </h3> </div> </div> </div> <p> The <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table provides information about <code class="literal"> InnoDB </code> performance and resource-related counters. </p> <p> <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table columns are shown below. For column descriptions, see <a class="xref" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> Section 28.4.21, “The INFORMATION_SCHEMA INNODB_METRICS Table” </a> . </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa80148274"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span><span class="token operator">=</span><span class="token string">"dml_inserts"</span> \G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> NAME<span class="token punctuation">:</span> dml_inserts SUBSYSTEM<span class="token punctuation">:</span> dml COUNT<span class="token punctuation">:</span> 46273 MAX_COUNT<span class="token punctuation">:</span> 46273 MIN_COUNT<span class="token punctuation">:</span> NULL AVG_COUNT<span class="token punctuation">:</span> 492.2659574468085 COUNT_RESET<span class="token punctuation">:</span> 46273 MAX_COUNT_RESET<span class="token punctuation">:</span> 46273 MIN_COUNT_RESET<span class="token punctuation">:</span> NULL AVG_COUNT_RESET<span class="token punctuation">:</span> NULL TIME_ENABLED<span class="token punctuation">:</span> 2014-11-28 16<span class="token punctuation">:</span>07<span class="token punctuation">:</span>53 TIME_DISABLED<span class="token punctuation">:</span> NULL TIME_ELAPSED<span class="token punctuation">:</span> 94 TIME_RESET<span class="token punctuation">:</span> NULL STATUS<span class="token punctuation">:</span> enabled TYPE<span class="token punctuation">:</span> status_counter COMMENT<span class="token punctuation">:</span> Number of rows inserted</span></code></pre> </div> <h4> <a name="idm46045149950272"> </a> Enabling, Disabling, and Resetting Counters </h4> <p> You can enable, disable, and reset counters using the following variables: </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_enable"> <code class="literal"> innodb_monitor_enable </code> </a> : Enables counters. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa17101821"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_monitor_enable <span class="token operator">=</span> <span class="token punctuation">[</span>counter<span class="token operator">-</span><span class="token keyword">name</span><span class="token operator">\|</span>module_name<span class="token operator">\|</span>pattern<span class="token operator">\|</span><span class="token keyword">all</span><span class="token punctuation">]</span><span class="token punctuation">;</span></code></pre> </div> </li> <li class="listitem"> <p> <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_disable"> <code class="literal"> innodb_monitor_disable </code> </a> : Disables counters. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa87494770"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_monitor_disable <span class="token operator">=</span> <span class="token punctuation">[</span>counter<span class="token operator">-</span><span class="token keyword">name</span><span class="token operator">\|</span>module_name<span class="token operator">\|</span>pattern<span class="token operator">\|</span><span class="token keyword">all</span><span class="token punctuation">]</span><span class="token punctuation">;</span></code></pre> </div> </li> <li class="listitem"> <p> <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_reset"> <code class="literal"> innodb_monitor_reset </code> </a> : Resets counter values to zero. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa80747560"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_monitor_reset <span class="token operator">=</span> <span class="token punctuation">[</span>counter<span class="token operator">-</span><span class="token keyword">name</span><span class="token operator">\|</span>module_name<span class="token operator">\|</span>pattern<span class="token operator">\|</span><span class="token keyword">all</span><span class="token punctuation">]</span><span class="token punctuation">;</span></code></pre> </div> </li> <li class="listitem"> <p> <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_reset_all"> <code class="literal"> innodb_monitor_reset_all </code> </a> : Resets all counter values. A counter must be disabled before using <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_reset_all"> <code class="literal"> innodb_monitor_reset_all </code> </a> . </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa1003410"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_monitor_reset_all <span class="token operator">=</span> <span class="token punctuation">[</span>counter<span class="token operator">-</span><span class="token keyword">name</span><span class="token operator">\|</span>module_name<span class="token operator">\|</span>pattern<span class="token operator">\|</span><span class="token keyword">all</span><span class="token punctuation">]</span><span class="token punctuation">;</span></code></pre> </div> </li> </ul> </div> <p> Counters and counter modules can also be enabled at startup using the MySQL server configuration file. For example, to enable the <code class="literal"> log </code> module, <code class="literal"> metadata_table_handles_opened </code> and <code class="literal"> metadata_table_handles_closed </code> counters, enter the following line in the <code class="literal"> [mysqld] </code> section of the MySQL server configuration file. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa64800018"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span> <span class="token constant">innodb_monitor_enable</span> <span class="token attr-value"><span class="token punctuation">=</span> log,metadata_table_handles_opened,metadata_table_handles_closed</span></code></pre> </div> <p> When enabling multiple counters or modules in a configuration file, specify the <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_enable"> <code class="literal"> innodb_monitor_enable </code> </a> variable followed by counter and module names separated by a comma, as shown above. Only the <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_enable"> <code class="literal"> innodb_monitor_enable </code> </a> variable can be used in a configuration file. The <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_disable"> <code class="literal"> innodb_monitor_disable </code> </a> and <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_reset"> <code class="literal"> innodb_monitor_reset </code> </a> variables are supported on the command line only. </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> Because each counter adds a degree of runtime overhead, use counters conservatively on production servers to diagnose specific issues or monitor specific functionality. A test or development server is recommended for more extensive use of counters. </p> </div> <h4> <a name="idm46045149923760"> </a> Counters </h4> <p> The list of available counters is subject to change. Query the Information Schema <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table for counters available in your MySQL server version. </p> <p> The counters enabled by default correspond to those shown in <a class="link" href="show-engine.html" title="15.7.7.16 SHOW ENGINE Statement"> <code class="literal"> SHOW ENGINE INNODB STATUS </code> </a> output. Counters shown in <a class="link" href="show-engine.html" title="15.7.7.16 SHOW ENGINE Statement"> <code class="literal"> SHOW ENGINE INNODB STATUS </code> </a> output are always enabled at a system level but can be disabled for the <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table. Counter status is not persistent. Unless configured otherwise, counters revert to their default enabled or disabled status when the server is restarted. </p> <p> If you run programs that would be affected by the addition or removal of counters, it is recommended that you review the releases notes and query the <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table to identify those changes as part of your upgrade process. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa91955213"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token keyword">name</span><span class="token punctuation">,</span> subsystem<span class="token punctuation">,</span> <span class="token keyword">status</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> <span class="token keyword">NAME</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> name <span class="token punctuation">\|</span> subsystem <span class="token punctuation">\|</span> status <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> adaptive_hash_pages_added <span class="token punctuation">\|</span> adaptive_hash_index <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> adaptive_hash_pages_removed <span class="token punctuation">\|</span> adaptive_hash_index <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> adaptive_hash_rows_added <span class="token punctuation">\|</span> adaptive_hash_index <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> adaptive_hash_rows_deleted_no_hash_entry <span class="token punctuation">\|</span> adaptive_hash_index <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> adaptive_hash_rows_removed <span class="token punctuation">\|</span> adaptive_hash_index <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> adaptive_hash_rows_updated <span class="token punctuation">\|</span> adaptive_hash_index <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> adaptive_hash_searches <span class="token punctuation">\|</span> adaptive_hash_index <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> adaptive_hash_searches_btree <span class="token punctuation">\|</span> adaptive_hash_index <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_data_reads <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_data_written <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_adaptive <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_adaptive_avg_pass <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_adaptive_avg_time_est <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_adaptive_avg_time_slot <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_adaptive_avg_time_thread <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_adaptive_pages <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_adaptive_total_pages <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_avg_page_rate <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_avg_pass <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_avg_time <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_background <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_background_pages <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_background_total_pages <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_batches <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_batch_num_scan <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_batch_pages <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_flush_batch_scanned <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> 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punctuation">\|</span> buffer_LRU_batch_flush_total_pages <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_LRU_batch_num_scan <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_LRU_batch_scanned <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_LRU_batch_scanned_per_call <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token 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class="token punctuation">\|</span> buffer_LRU_unzip_search_scanned_per_call <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pages_created <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pages_read <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pages_written <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token 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buffer_page_io <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_page_written_index_leaf <span class="token punctuation">\|</span> buffer_page_io <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_page_written_index_non_leaf <span class="token punctuation">\|</span> buffer_page_io <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_page_written_on_log_no_waits <span class="token punctuation">\|</span> buffer_page_io <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_page_written_on_log_waits 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buffer_page_written_system_page <span class="token punctuation">\|</span> buffer_page_io <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_page_written_trx_system <span class="token punctuation">\|</span> buffer_page_io <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_page_written_undo_log <span class="token punctuation">\|</span> buffer_page_io <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_page_written_xdes <span class="token punctuation">\|</span> buffer_page_io <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token 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punctuation">\|</span> buffer_pool_pages_data <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_pages_dirty <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_pages_free <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_pages_misc <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_pages_total <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_reads <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_read_ahead <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_read_ahead_evicted <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_read_requests <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_size <span class="token punctuation">\|</span> server <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_wait_free <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> buffer_pool_write_requests <span class="token punctuation">\|</span> buffer <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> compression_pad_decrements <span class="token punctuation">\|</span> 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class="token punctuation">\|</span> log_on_write_no_waits <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_on_write_waits <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_on_write_wait_loops <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_padded <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_partial_block_writes <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_waits <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_writer_no_waits <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_writer_on_archiver_waits <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_writer_on_file_space_waits <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_writer_waits <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_writer_wait_loops <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_writes <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_write_notifier_no_waits <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_write_notifier_waits <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_write_notifier_wait_loops <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_write_requests <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> log_write_to_file_requests_interval <span class="token punctuation">\|</span> log <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> metadata_table_handles_closed <span class="token punctuation">\|</span> metadata <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> metadata_table_handles_opened <span class="token punctuation">\|</span> metadata <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> metadata_table_reference_count <span class="token punctuation">\|</span> metadata <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> module_cpu <span class="token punctuation">\|</span> cpu <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> module_dblwr <span class="token punctuation">\|</span> dblwr <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> module_page_track <span class="token punctuation">\|</span> page_track <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> os_data_fsyncs <span class="token punctuation">\|</span> os <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> os_data_reads <span class="token punctuation">\|</span> os <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> os_data_writes <span class="token punctuation">\|</span> os <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> os_log_bytes_written <span class="token punctuation">\|</span> os <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> os_log_fsyncs <span class="token punctuation">\|</span> os <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> os_log_pending_fsyncs <span class="token punctuation">\|</span> os <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> os_log_pending_writes <span class="token punctuation">\|</span> os <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> os_pending_reads <span class="token punctuation">\|</span> os <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> os_pending_writes <span class="token punctuation">\|</span> os <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> page_track_checkpoint_partial_flush_request <span class="token punctuation">\|</span> page_track <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> page_track_full_block_writes <span class="token punctuation">\|</span> page_track <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> page_track_partial_block_writes <span class="token punctuation">\|</span> page_track <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> page_track_resets <span class="token punctuation">\|</span> page_track <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> purge_del_mark_records <span class="token punctuation">\|</span> purge <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> purge_dml_delay_usec <span class="token punctuation">\|</span> purge <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> purge_invoked <span class="token punctuation">\|</span> purge <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> purge_resume_count <span class="token punctuation">\|</span> purge <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> purge_stop_count <span class="token punctuation">\|</span> purge <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> purge_truncate_history_count <span class="token punctuation">\|</span> purge <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> purge_truncate_history_usec <span class="token punctuation">\|</span> purge <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> purge_undo_log_pages <span class="token punctuation">\|</span> purge <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> purge_upd_exist_or_extern_records <span class="token punctuation">\|</span> purge <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> sampled_pages_read <span class="token punctuation">\|</span> sampling <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> sampled_pages_skipped <span class="token punctuation">\|</span> sampling <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_active_transactions <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_allocations <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_commits_insert_update <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_nl_ro_commits <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_on_log_no_waits <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_on_log_waits <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_on_log_wait_loops <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_rollbacks <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_rollbacks_savepoint <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_rollback_active <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_ro_commits <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_rseg_current_size <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_rseg_history_len <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_rw_commits <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_undo_slots_cached <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> trx_undo_slots_used <span class="token punctuation">\|</span> transaction <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> undo_truncate_count <span class="token punctuation">\|</span> undo <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> undo_truncate_done_logging_count <span class="token punctuation">\|</span> undo <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> undo_truncate_start_logging_count <span class="token punctuation">\|</span> undo <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> undo_truncate_usec <span class="token punctuation">\|</span> undo <span class="token punctuation">\|</span> disabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output">314 rows in set (0.00 sec)</span></code></pre> </div> <h4> <a name="idm46045149884192"> </a> Counter Modules </h4> <p> Each counter is associated with a particular module. Module names can be used to enable, disable, or reset all counters for a particular subsystem. For example, use <code class="literal"> module_dml </code> to enable all counters associated with the <code class="literal"> dml </code> subsystem. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30337191"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_monitor_enable <span class="token operator">=</span> module_dml<span class="token punctuation">;</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token keyword">name</span><span class="token punctuation">,</span> subsystem<span class="token punctuation">,</span> <span class="token keyword">status</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">WHERE</span> subsystem <span class="token operator">=</span><span class="token string">'dml'</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> name <span class="token punctuation">\|</span> subsystem <span class="token punctuation">\|</span> status <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> dml_reads <span class="token punctuation">\|</span> dml <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> dml_inserts <span class="token punctuation">\|</span> dml <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> dml_deletes <span class="token punctuation">\|</span> dml <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">\|</span> dml_updates <span class="token punctuation">\|</span> dml <span class="token punctuation">\|</span> enabled <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> <p> Module names can be used with <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_enable"> <code class="literal"> innodb_monitor_enable </code> </a> and related variables. </p> <p> Module names and corresponding <code class="literal"> SUBSYSTEM </code> names are listed below. </p> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> <code class="literal"> module_adaptive_hash </code> (subsystem = <code class="literal"> adaptive_hash_index </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_buffer </code> (subsystem = <code class="literal"> buffer </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_buffer_page </code> (subsystem = <code class="literal"> buffer_page_io </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_compress </code> (subsystem = <code class="literal"> compression </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_ddl </code> (subsystem = <code class="literal"> ddl </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_dml </code> (subsystem = <code class="literal"> dml </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_file </code> (subsystem = <code class="literal"> file_system </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_ibuf_system </code> (subsystem = <code class="literal"> change_buffer </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_icp </code> (subsystem = <code class="literal"> icp </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_index </code> (subsystem = <code class="literal"> index </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_innodb </code> (subsystem = <code class="literal"> innodb </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_lock </code> (subsystem = <code class="literal"> lock </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_log </code> (subsystem = <code class="literal"> log </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_metadata </code> (subsystem = <code class="literal"> metadata </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_os </code> (subsystem = <code class="literal"> os </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_purge </code> (subsystem = <code class="literal"> purge </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_trx </code> (subsystem = <code class="literal"> transaction </code> ) </p> </li> <li class="listitem"> <p> <code class="literal"> module_undo </code> (subsystem = <code class="literal"> undo </code> ) </p> </li> </ul> </div> <div class="example"> <a name="innodb-information-schema-metrics-table-example"> </a> <p class="title"> <b> Example 17.11 Working with INNODB_METRICS Table Counters </b> </p> <div class="example-contents"> <p> This example demonstrates enabling, disabling, and resetting a counter, and querying counter data in the <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table. </p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p> Create a simple <code class="literal"> InnoDB </code> table: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa94391970"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">USE</span> test<span class="token punctuation">;</span> <span class="token keyword">Database</span> <span class="token keyword">changed</span> <span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span>c1 <span class="token datatype">INT</span><span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span>INNODB<span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.02 sec)</span></code></pre> </div> </li> <li class="listitem"> <p> Enable the <code class="literal"> dml_inserts </code> counter. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3611800"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_monitor_enable <span class="token operator">=</span> dml_inserts<span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.01 sec)</span></code></pre> </div> <p> A description of the <code class="literal"> dml_inserts </code> counter can be found in the <code class="literal"> COMMENT </code> column of the <code class="literal"> INNODB_METRICS </code> table: </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46185012"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token keyword">NAME</span><span class="token punctuation">,</span> <span class="token keyword">COMMENT</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span><span class="token operator">=</span><span class="token string">"dml_inserts"</span><span class="token punctuation">;</span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> NAME <span class="token punctuation">\|</span> COMMENT <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span> <span class="token output"><span class="token punctuation">\|</span> dml_inserts <span class="token punctuation">\|</span> Number of rows inserted <span class="token punctuation">\|</span></span> <span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre> </div> </li> <li class="listitem"> <p> Query the <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table for the <code class="literal"> dml_inserts </code> counter data. Because no DML operations have been performed, the counter values are zero or NULL. The <code class="literal"> TIME_ENABLED </code> and <code class="literal"> TIME_ELAPSED </code> values indicate when the counter was last enabled and how many seconds have elapsed since that time. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa84259900"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span><span class="token operator">=</span><span class="token string">"dml_inserts"</span> \G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> NAME<span class="token punctuation">:</span> dml_inserts SUBSYSTEM<span class="token punctuation">:</span> dml COUNT<span class="token punctuation">:</span> 0 MAX_COUNT<span class="token punctuation">:</span> 0 MIN_COUNT<span class="token punctuation">:</span> NULL AVG_COUNT<span class="token punctuation">:</span> 0 COUNT_RESET<span class="token punctuation">:</span> 0 MAX_COUNT_RESET<span class="token punctuation">:</span> 0 MIN_COUNT_RESET<span class="token punctuation">:</span> NULL AVG_COUNT_RESET<span class="token punctuation">:</span> NULL TIME_ENABLED<span class="token punctuation">:</span> 2014-12-04 14<span class="token punctuation">:</span>18<span class="token punctuation">:</span>28 TIME_DISABLED<span class="token punctuation">:</span> NULL TIME_ELAPSED<span class="token punctuation">:</span> 28 TIME_RESET<span class="token punctuation">:</span> NULL STATUS<span class="token punctuation">:</span> enabled TYPE<span class="token punctuation">:</span> status_counter COMMENT<span class="token punctuation">:</span> Number of rows inserted</span></code></pre> </div> </li> <li class="listitem"> <p> Insert three rows of data into the table. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa20749815"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <span class="token keyword">values</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 1 row affected (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <span class="token keyword">values</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 1 row affected (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <span class="token keyword">values</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token output">Query OK, 1 row affected (0.00 sec)</span></code></pre> </div> </li> <li class="listitem"> <p> Query the <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table again for the <code class="literal"> dml_inserts </code> counter data. A number of counter values have now incremented including <code class="literal"> COUNT </code> , <code class="literal"> MAX_COUNT </code> , <code class="literal"> AVG_COUNT </code> , and <code class="literal"> COUNT_RESET </code> . Refer to the <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table definition for descriptions of these values. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa43876000"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span><span class="token operator">=</span><span class="token string">"dml_inserts"</span>\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> NAME<span class="token punctuation">:</span> dml_inserts SUBSYSTEM<span class="token punctuation">:</span> dml COUNT<span class="token punctuation">:</span> 3 MAX_COUNT<span class="token punctuation">:</span> 3 MIN_COUNT<span class="token punctuation">:</span> NULL AVG_COUNT<span class="token punctuation">:</span> 0.046153846153846156 COUNT_RESET<span class="token punctuation">:</span> 3 MAX_COUNT_RESET<span class="token punctuation">:</span> 3 MIN_COUNT_RESET<span class="token punctuation">:</span> NULL AVG_COUNT_RESET<span class="token punctuation">:</span> NULL TIME_ENABLED<span class="token punctuation">:</span> 2014-12-04 14<span class="token punctuation">:</span>18<span class="token punctuation">:</span>28 TIME_DISABLED<span class="token punctuation">:</span> NULL TIME_ELAPSED<span class="token punctuation">:</span> 65 TIME_RESET<span class="token punctuation">:</span> NULL STATUS<span class="token punctuation">:</span> enabled TYPE<span class="token punctuation">:</span> status_counter COMMENT<span class="token punctuation">:</span> Number of rows inserted</span></code></pre> </div> </li> <li class="listitem"> <p> Reset the <code class="literal"> dml_inserts </code> counter and query the <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table again for the <code class="literal"> dml_inserts </code> counter data. The <code class="literal"> %_RESET </code> values that were reported previously, such as <code class="literal"> COUNT_RESET </code> and <code class="literal"> MAX_RESET </code> , are set back to zero. Values such as <code class="literal"> COUNT </code> , <code class="literal"> MAX_COUNT </code> , and <code class="literal"> AVG_COUNT </code> , which cumulatively collect data from the time the counter is enabled, are unaffected by the reset. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa24772519"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_monitor_reset <span class="token operator">=</span> dml_inserts<span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span><span class="token operator">=</span><span class="token string">"dml_inserts"</span>\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> NAME<span class="token punctuation">:</span> dml_inserts SUBSYSTEM<span class="token punctuation">:</span> dml COUNT<span class="token punctuation">:</span> 3 MAX_COUNT<span class="token punctuation">:</span> 3 MIN_COUNT<span class="token punctuation">:</span> NULL AVG_COUNT<span class="token punctuation">:</span> 0.03529411764705882 COUNT_RESET<span class="token punctuation">:</span> 0 MAX_COUNT_RESET<span class="token punctuation">:</span> 0 MIN_COUNT_RESET<span class="token punctuation">:</span> NULL AVG_COUNT_RESET<span class="token punctuation">:</span> 0 TIME_ENABLED<span class="token punctuation">:</span> 2014-12-04 14<span class="token punctuation">:</span>18<span class="token punctuation">:</span>28 TIME_DISABLED<span class="token punctuation">:</span> NULL TIME_ELAPSED<span class="token punctuation">:</span> 85 TIME_RESET<span class="token punctuation">:</span> 2014-12-04 14<span class="token punctuation">:</span>19<span class="token punctuation">:</span>44 STATUS<span class="token punctuation">:</span> enabled TYPE<span class="token punctuation">:</span> status_counter COMMENT<span class="token punctuation">:</span> Number of rows inserted</span></code></pre> </div> </li> <li class="listitem"> <p> To reset all counter values, you must first disable the counter. Disabling the counter sets the <code class="literal"> STATUS </code> value to <code class="literal"> disabled </code> . </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa67105841"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_monitor_disable <span class="token operator">=</span> dml_inserts<span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span><span class="token operator">=</span><span class="token string">"dml_inserts"</span>\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> NAME<span class="token punctuation">:</span> dml_inserts SUBSYSTEM<span class="token punctuation">:</span> dml COUNT<span class="token punctuation">:</span> 3 MAX_COUNT<span class="token punctuation">:</span> 3 MIN_COUNT<span class="token punctuation">:</span> NULL AVG_COUNT<span class="token punctuation">:</span> 0.030612244897959183 COUNT_RESET<span class="token punctuation">:</span> 0 MAX_COUNT_RESET<span class="token punctuation">:</span> 0 MIN_COUNT_RESET<span class="token punctuation">:</span> NULL AVG_COUNT_RESET<span class="token punctuation">:</span> 0 TIME_ENABLED<span class="token punctuation">:</span> 2014-12-04 14<span class="token punctuation">:</span>18<span class="token punctuation">:</span>28 TIME_DISABLED<span class="token punctuation">:</span> 2014-12-04 14<span class="token punctuation">:</span>20<span class="token punctuation">:</span>06 TIME_ELAPSED<span class="token punctuation">:</span> 98 TIME_RESET<span class="token punctuation">:</span> NULL STATUS<span class="token punctuation">:</span> disabled TYPE<span class="token punctuation">:</span> status_counter COMMENT<span class="token punctuation">:</span> Number of rows inserted</span></code></pre> </div> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> <p> Wildcard match is supported for counter and module names. For example, instead of specifying the full <code class="literal"> dml_inserts </code> counter name, you can specify <code class="literal"> dml_i% </code> . You can also enable, disable, or reset multiple counters or modules at once using a wildcard match. For example, specify <code class="literal"> dml_% </code> to enable, disable, or reset all counters that begin with <code class="literal"> dml_ </code> . </p> </div> </li> <li class="listitem"> <p> After the counter is disabled, you can reset all counter values using the <a class="link" href="innodb-parameters.html#sysvar_innodb_monitor_reset_all"> <code class="literal"> innodb_monitor_reset_all </code> </a> option. All values are set to zero or NULL. </p> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa53861441"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_monitor_reset_all <span class="token operator">=</span> dml_inserts<span class="token punctuation">;</span> <span class="token output">Query OK, 0 rows affected (0.00 sec)</span> <span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator"></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_METRICS <span class="token keyword">WHERE</span> <span class="token keyword">NAME</span><span class="token operator">=</span><span class="token string">"dml_inserts"</span>\G <span class="token output"><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> 1. row <span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span><span class="token punctuation"></span> NAME<span class="token punctuation">:</span> dml_inserts SUBSYSTEM<span class="token punctuation">:</span> dml COUNT<span class="token punctuation">:</span> 0 MAX_COUNT<span class="token punctuation">:</span> NULL MIN_COUNT<span class="token punctuation">:</span> NULL AVG_COUNT<span class="token punctuation">:</span> NULL COUNT_RESET<span class="token punctuation">:</span> 0 MAX_COUNT_RESET<span class="token punctuation">:</span> NULL MIN_COUNT_RESET<span class="token punctuation">:</span> NULL AVG_COUNT_RESET<span class="token punctuation">:</span> NULL TIME_ENABLED<span class="token punctuation">:</span> NULL TIME_DISABLED<span class="token punctuation">:</span> NULL TIME_ELAPSED<span class="token punctuation">:</span> NULL TIME_RESET<span class="token punctuation">:</span> NULL STATUS<span class="token punctuation">:</span> disabled TYPE<span class="token punctuation">:</span> status_counter COMMENT<span class="token punctuation">:</span> Number of rows inserted</span></code></pre> </div> </li> </ol> </div> </div> </div> <br class="example-break"/> </div> <br/> </div>

https://dev.mysql.com/doc/refman/8.4/en/performance-schema-cond-instances-table.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="performance-schema-cond-instances-table"> </a> 29.12.3.1 The cond_instances Table </h4> </div> </div> </div> <a class="indexterm" name="idm46045073599312"> </a> <a class="indexterm" name="idm46045073597824"> </a> The <a class="link" href="performance-schema-cond-instances-table.html" title="29.12.3.1 The cond_instances Table"> <code class="literal"> cond_instances </code> </a> table lists all the conditions seen by the Performance Schema while the server executes. A condition is a synchronization mechanism used in the code to signal that a specific event has happened, so that a thread waiting for this condition can resume work. When a thread is waiting for something to happen, the condition name is an indication of what the thread is waiting for, but there is no immediate way to tell which other thread, or threads, causes the condition to happen. The <a class="link" href="performance-schema-cond-instances-table.html" title="29.12.3.1 The cond_instances Table"> <code class="literal"> cond_instances </code> </a> table has these columns: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> NAME </code> The instrument name associated with the condition. </li> <li class="listitem"> <code class="literal"> OBJECT_INSTANCE_BEGIN </code> The address in memory of the instrumented condition. </li> </ul> </div> The <a class="link" href="performance-schema-cond-instances-table.html" title="29.12.3.1 The cond_instances Table"> <code class="literal"> cond_instances </code> </a> table has these indexes: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> Primary key on ( <code class="literal"> OBJECT_INSTANCE_BEGIN </code> ) </li> <li class="listitem"> Index on ( <code class="literal"> NAME </code> ) </li> </ul> </div> <a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement"> <code class="literal"> TRUNCATE TABLE </code> </a> is not permitted for the <a class="link" href="performance-schema-cond-instances-table.html" title="29.12.3.1 The cond_instances Table"> <code class="literal"> cond_instances </code> </a> table. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/innodb-file-per-table-tablespaces.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="innodb-file-per-table-tablespaces"> </a> 17.6.3.2 File-Per-Table Tablespaces </h4> </div> </div> </div> <a class="indexterm" name="idm46045165503168"> </a> <a class="indexterm" name="idm46045165501664"> </a> A file-per-table tablespace contains data and indexes for a single <code class="literal"> InnoDB </code> table, and is stored on the file system in a single data file. File-per-table tablespace characteristics are described under the following topics in this section: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <a class="xref" href="innodb-file-per-table-tablespaces.html#innodb-file-per-table-configuration" title="File-Per-Table Tablespace Configuration"> File-Per-Table Tablespace Configuration </a> </li> <li class="listitem"> <a class="xref" href="innodb-file-per-table-tablespaces.html#innodb-file-per-table-data-files" title="File-Per-Table Tablespace Data Files"> File-Per-Table Tablespace Data Files </a> </li> <li class="listitem"> <a class="xref" href="innodb-file-per-table-tablespaces.html#innodb-file-per-table-advantages" title="File-Per-Table Tablespace Advantages"> File-Per-Table Tablespace Advantages </a> </li> <li class="listitem"> <a class="xref" href="innodb-file-per-table-tablespaces.html#innodb-file-per-table-disadvantages" title="File-Per-Table Tablespace Disadvantages"> File-Per-Table Tablespace Disadvantages </a> </li> </ul> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="innodb-file-per-table-configuration"> </a> File-Per-Table Tablespace Configuration </h5> </div> </div> </div> <code class="literal"> InnoDB </code> creates tables in file-per-table tablespaces by default. This behavior is controlled by the <a class="link" href="innodb-parameters.html#sysvar_innodb_file_per_table"> <code class="literal"> innodb_file_per_table </code> </a> variable. Disabling <a class="link" href="innodb-parameters.html#sysvar_innodb_file_per_table"> <code class="literal"> innodb_file_per_table </code> </a> causes <code class="literal"> InnoDB </code> to create tables in the system tablespace. An <a class="link" href="innodb-parameters.html#sysvar_innodb_file_per_table"> <code class="literal"> innodb_file_per_table </code> </a> setting can be specified in an option file or configured at runtime using a <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment"> <code class="literal"> SET GLOBAL </code> </a> statement. Changing the setting at runtime requires privileges sufficient to set global system variables. See <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges"> Section 7.1.9.1, “System Variable Privileges” </a> . Option file: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa89140588"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-ini">[mysqld] innodb_file_per_table=ON</code></pre> </div> Using <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment"> <code class="literal"> SET GLOBAL </code> </a> at runtime: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa10292868"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SET GLOBAL innodb_file_per_table=ON;</code></pre> </div> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="innodb-file-per-table-data-files"> </a> File-Per-Table Tablespace Data Files </h5> </div> </div> </div> A file-per-table tablespace is created in an <code class="filename"> .ibd </code> data file in a schema directory under the MySQL data directory. The <code class="filename"> .ibd </code> file is named for the table ( <code class="filename"> <code> table_name </code> .ibd </code> ). For example, the data file for table <code class="literal"> test.t1 </code> is created in the <code class="filename"> test </code> directory under the MySQL data directory: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34238097"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> USE test; mysql> CREATE TABLE t1 ( -> id INT PRIMARY KEY AUTO_INCREMENT, -> name VARCHAR(100) -> ) ENGINE = InnoDB; mysql> EXIT;</code></pre> </div> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa73359084"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-terminal">$> cd /path/to/mysql/data/test $> ls t1.ibd</code></pre> </div> You can use the <code class="literal"> DATA DIRECTORY </code> clause of the <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement"> <code class="literal"> CREATE TABLE </code> </a> statement to implicitly create a file-per-table tablespace data file outside of the data directory. For more information, see <a class="xref" href="innodb-create-table-external.html" title="17.6.1.2 Creating Tables Externally"> Section 17.6.1.2, “Creating Tables Externally” </a> . </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="innodb-file-per-table-advantages"> </a> File-Per-Table Tablespace Advantages </h5> </div> </div> </div> File-per-table tablespaces have the following advantages over shared tablespaces such as the system tablespace or general tablespaces. <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> Disk space is returned to the operating system after truncating or dropping a table created in a file-per-table tablespace. Truncating or dropping a table stored in a shared tablespace creates free space within the shared tablespace data file, which can only be used for <code class="literal"> InnoDB </code> data. In other words, a shared tablespace data file does not shrink in size after a table is truncated or dropped. </li> <li class="listitem"> A table-copying <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> operation on a table that resides in a shared tablespace can increase the amount of disk space occupied by the tablespace. Such operations may require as much additional space as the data in the table plus indexes. This space is not released back to the operating system as it is for file-per-table tablespaces. </li> <li class="listitem"> <a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement"> <code class="literal"> TRUNCATE TABLE </code> </a> performance is better when executed on tables that reside in file-per-table tablespaces. </li> <li class="listitem"> File-per-table tablespace data files can be created on separate storage devices for I/O optimization, space management, or backup purposes. See <a class="xref" href="innodb-create-table-external.html" title="17.6.1.2 Creating Tables Externally"> Section 17.6.1.2, “Creating Tables Externally” </a> . </li> <li class="listitem"> You can import a table that resides in file-per-table tablespace from another MySQL instance. See <a class="xref" href="innodb-table-import.html" title="17.6.1.3 Importing InnoDB Tables"> Section 17.6.1.3, “Importing InnoDB Tables” </a> . </li> <li class="listitem"> Tables created in file-per-table tablespaces support features associated with <code class="literal"> DYNAMIC </code> and <code class="literal"> COMPRESSED </code> row formats, which are not supported by the system tablespace. See <a class="xref" href="innodb-row-format.html" title="17.10 InnoDB Row Formats"> Section 17.10, “InnoDB Row Formats” </a> . </li> <li class="listitem"> Tables stored in individual tablespace data files can save time and improve chances for a successful recovery when data corruption occurs, when backups or binary logs are unavailable, or when the MySQL server instance cannot be restarted. </li> <li class="listitem"> Tables created in file-per-table tablespaces can be backed up or restored quickly using MySQL Enterprise Backup, without interrupting the use of other <code class="literal"> InnoDB </code> tables. This is beneficial for tables on varying backup schedules or that require backup less frequently. See <a class="ulink" href="/doc/mysql-enterprise-backup/8.4/en/partial.html" target="_top"> Making a Partial Backup </a> for details. </li> <li class="listitem"> File-per-table tablespaces permit monitoring table size on the file system by monitoring the size of the tablespace data file. </li> <li class="listitem"> Common Linux file systems do not permit concurrent writes to a single file such as a shared tablespace data file when <a class="link" href="innodb-parameters.html#sysvar_innodb_flush_method"> <code class="literal"> innodb_flush_method </code> </a> is set to <code class="literal"> O_DIRECT </code> . As a result, there are possible performance improvements when using file-per-table tablespaces in conjunction with this setting. </li> <li class="listitem"> Tables in a shared tablespace are limited in size by the 64TB tablespace size limit. By comparison, each file-per-table tablespace has a 64TB size limit, which provides plenty of room for individual tables to grow in size. </li> </ul> </div> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="innodb-file-per-table-disadvantages"> </a> File-Per-Table Tablespace Disadvantages </h5> </div> </div> </div> File-per-table tablespaces have the following disadvantages compared to shared tablespaces such as the system tablespace or general tablespaces. <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> With file-per-table tablespaces, each table may have unused space that can only be utilized by rows of the same table, which can lead to wasted space if not properly managed. </li> <li class="listitem"> <code class="literal"> fsync </code> operations are performed on multiple file-per-table data files instead of a single shared tablespace data file. Because <code class="literal"> fsync </code> operations are per file, write operations for multiple tables cannot be combined, which can result in a higher total number of <code class="literal"> fsync </code> operations. </li> <li class="listitem"> <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server"> mysqld </a> must keep an open file handle for each file-per-table tablespace, which may impact performance if you have numerous tables in file-per-table tablespaces. </li> <li class="listitem"> More file descriptors are required when each table has its own data file. </li> <li class="listitem"> There is potential for more fragmentation, which can impede <a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement"> <code class="literal"> DROP TABLE </code> </a> and table scan performance. However, if fragmentation is managed, file-per-table tablespaces can improve performance for these operations. </li> <li class="listitem"> The buffer pool is scanned when dropping a table that resides in a file-per-table tablespace, which can take several seconds for large buffer pools. The scan is performed with a broad internal lock, which may delay other operations. </li> <li class="listitem"> The <a class="link" href="innodb-parameters.html#sysvar_innodb_autoextend_increment"> <code class="literal"> innodb_autoextend_increment </code> </a> variable, which defines the increment size for extending the size of an auto-extending shared tablespace file when it becomes full, does not apply to file-per-table tablespace files, which are auto-extending regardless of the <a class="link" href="innodb-parameters.html#sysvar_innodb_autoextend_increment"> <code class="literal"> innodb_autoextend_increment </code> </a> setting. Initial file-per-table tablespace extensions are by small amounts, after which extensions occur in increments of 4MB. </li> </ul> </div> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/do.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="do"> </a> 15.2.3 DO Statement </h3> </div> </div> </div> <a class="indexterm" name="idm46045182811488"> </a> <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa67072904"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">DO expr [, expr] ...</code></pre> </div> <a class="link" href="do.html" title="15.2.3 DO Statement"> <code class="literal"> DO </code> </a> executes the expressions but does not return any results. In most respects, <a class="link" href="do.html" title="15.2.3 DO Statement"> <code class="literal"> DO </code> </a> is shorthand for <code class="literal"> SELECT <code> expr </code> , ... </code> , but has the advantage that it is slightly faster when you do not care about the result. <a class="link" href="do.html" title="15.2.3 DO Statement"> <code class="literal"> DO </code> </a> is useful primarily with functions that have side effects, such as <a class="link" href="locking-functions.html#function_release-lock"> <code class="literal"> RELEASE_LOCK() </code> </a> . Example: This <a class="link" href="select.html" title="15.2.13 SELECT Statement"> <code class="literal"> SELECT </code> </a> statement pauses, but also produces a result set: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47891606"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT SLEEP(5); +----------+ | SLEEP(5) | +----------+ | 0 | +----------+ 1 row in set (5.02 sec)</code></pre> </div> <a class="link" href="do.html" title="15.2.3 DO Statement"> <code class="literal"> DO </code> </a> , on the other hand, pauses without producing a result set.: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa21997559"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> DO SLEEP(5); Query OK, 0 rows affected (4.99 sec)</code></pre> </div> This could be useful, for example in a stored function or trigger, which prohibit statements that produce result sets. <a class="link" href="do.html" title="15.2.3 DO Statement"> <code class="literal"> DO </code> </a> only executes expressions. It cannot be used in all cases where <code class="literal"> SELECT </code> can be used. For example, <code class="literal"> DO id FROM t1 </code> is invalid because it references a table. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/index-page-merge-threshold.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="index-page-merge-threshold"> </a> 17.8.11 Configuring the Merge Threshold for Index Pages </h3> </div> </div> </div> You can configure the <code class="literal"> MERGE_THRESHOLD </code> value for index pages. If the “ page-full ” percentage for an index page falls below the <code class="literal"> MERGE_THRESHOLD </code> value when a row is deleted or when a row is shortened by an <a class="link" href="update.html" title="15.2.17 UPDATE Statement"> <code class="literal"> UPDATE </code> </a> operation, <code class="literal"> InnoDB </code> attempts to merge the index page with a neighboring index page. The default <code class="literal"> MERGE_THRESHOLD </code> value is 50, which is the previously hardcoded value. The minimum <code class="literal"> MERGE_THRESHOLD </code> value is 1 and the maximum value is 50. When the “ page-full ” percentage for an index page falls below 50%, which is the default <code class="literal"> MERGE_THRESHOLD </code> setting, <code class="literal"> InnoDB </code> attempts to merge the index page with a neighboring page. If both pages are close to 50% full, a page split can occur soon after the pages are merged. If this merge-split behavior occurs frequently, it can have an adverse affect on performance. To avoid frequent merge-splits, you can lower the <code class="literal"> MERGE_THRESHOLD </code> value so that <code class="literal"> InnoDB </code> attempts page merges at a lower “ page-full ” percentage. Merging pages at a lower page-full percentage leaves more room in index pages and helps reduce merge-split behavior. The <code class="literal"> MERGE_THRESHOLD </code> for index pages can be defined for a table or for individual indexes. A <code class="literal"> MERGE_THRESHOLD </code> value defined for an individual index takes priority over a <code class="literal"> MERGE_THRESHOLD </code> value defined for the table. If undefined, the <code class="literal"> MERGE_THRESHOLD </code> value defaults to 50. <h4> <a name="idm46045161921136"> </a> Setting MERGE_THRESHOLD for a Table </h4> You can set the <code class="literal"> MERGE_THRESHOLD </code> value for a table using the <code> table_option </code> <code class="literal"> COMMENT </code> clause of the <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement"> <code class="literal"> CREATE TABLE </code> </a> statement. For example: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44551888"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">CREATE TABLE t1 ( id INT, KEY id_index (id) ) COMMENT='MERGE_THRESHOLD=45';</code></pre> </div> You can also set the <code class="literal"> MERGE_THRESHOLD </code> value for an existing table using the <code> table_option </code> <code class="literal"> COMMENT </code> clause with <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> : <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa77746136"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">CREATE TABLE t1 ( id INT, KEY id_index (id) ); ALTER TABLE t1 COMMENT='MERGE_THRESHOLD=40';</code></pre> </div> <h4> <a name="idm46045161911328"> </a> Setting MERGE_THRESHOLD for Individual Indexes </h4> To set the <code class="literal"> MERGE_THRESHOLD </code> value for an individual index, you can use the <code> index_option </code> <code class="literal"> COMMENT </code> clause with <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement"> <code class="literal"> CREATE TABLE </code> </a> , <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> , or <a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement"> <code class="literal"> CREATE INDEX </code> </a> , as shown in the following examples: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> Setting <code class="literal"> MERGE_THRESHOLD </code> for an individual index using <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement"> <code class="literal"> CREATE TABLE </code> </a> : <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60266295"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">CREATE TABLE t1 ( id INT, KEY id_index (id) COMMENT 'MERGE_THRESHOLD=40' );</code></pre> </div> </li> <li class="listitem"> Setting <code class="literal"> MERGE_THRESHOLD </code> for an individual index using <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> : <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa31890012"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">CREATE TABLE t1 ( id INT, KEY id_index (id) ); ALTER TABLE t1 DROP KEY id_index; ALTER TABLE t1 ADD KEY id_index (id) COMMENT 'MERGE_THRESHOLD=40';</code></pre> </div> </li> <li class="listitem"> Setting <code class="literal"> MERGE_THRESHOLD </code> for an individual index using <a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement"> <code class="literal"> CREATE INDEX </code> </a> : <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa92262354"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">CREATE TABLE t1 (id INT); CREATE INDEX id_index ON t1 (id) COMMENT 'MERGE_THRESHOLD=40';</code></pre> </div> </li> </ul> </div> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> You cannot modify the <code class="literal"> MERGE_THRESHOLD </code> value at the index level for <code class="literal"> GEN_CLUST_INDEX </code> , which is the clustered index created by <code class="literal"> InnoDB </code> when an <code class="literal"> InnoDB </code> table is created without a primary key or unique key index. You can only modify the <code class="literal"> MERGE_THRESHOLD </code> value for <code class="literal"> GEN_CLUST_INDEX </code> by setting <code class="literal"> MERGE_THRESHOLD </code> for the table. </div> <h4> <a name="idm46045161886736"> </a> Querying the MERGE_THRESHOLD Value for an Index </h4> The current <code class="literal"> MERGE_THRESHOLD </code> value for an index can be obtained by querying the <a class="link" href="information-schema-innodb-indexes-table.html" title="28.4.20 The INFORMATION_SCHEMA INNODB_INDEXES Table"> <code class="literal"> INNODB_INDEXES </code> </a> table. For example: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa50025705"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_INDEXES WHERE NAME='id_index' \G *************************** 1. row *************************** INDEX_ID: 91 NAME: id_index TABLE_ID: 68 TYPE: 0 N_FIELDS: 1 PAGE_NO: 4 SPACE: 57 MERGE_THRESHOLD: 40</code></pre> </div> You can use <a class="link" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement"> <code class="literal"> SHOW CREATE TABLE </code> </a> to view the <code class="literal"> MERGE_THRESHOLD </code> value for a table, if explicitly defined using the <code> table_option </code> <code class="literal"> COMMENT </code> clause: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa97733350"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SHOW CREATE TABLE t2 \G *************************** 1. row *************************** Table: t2 Create Table: CREATE TABLE `t2` ( `id` int(11) DEFAULT NULL, KEY `id_index` (`id`) COMMENT 'MERGE_THRESHOLD=40' ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci</code></pre> </div> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> A <code class="literal"> MERGE_THRESHOLD </code> value defined at the index level takes priority over a <code class="literal"> MERGE_THRESHOLD </code> value defined for the table. If undefined, <code class="literal"> MERGE_THRESHOLD </code> defaults to 50% ( <code class="literal"> MERGE_THRESHOLD=50 </code> , which is the previously hardcoded value. </div> Likewise, you can use <a class="link" href="show-index.html" title="15.7.7.23 SHOW INDEX Statement"> <code class="literal"> SHOW INDEX </code> </a> to view the <code class="literal"> MERGE_THRESHOLD </code> value for an index, if explicitly defined using the <code> index_option </code> <code class="literal"> COMMENT </code> clause: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa86304780"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SHOW INDEX FROM t2 \G *************************** 1. row *************************** Table: t2 Non_unique: 1 Key_name: id_index Seq_in_index: 1 Column_name: id Collation: A Cardinality: 0 Sub_part: NULL Packed: NULL Null: YES Index_type: BTREE Comment: Index_comment: MERGE_THRESHOLD=40</code></pre> </div> <h4> <a name="idm46045161866784"> </a> Measuring the Effect of MERGE_THRESHOLD Settings </h4> The <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> table provides two counters that can be used to measure the effect of a <code class="literal"> MERGE_THRESHOLD </code> setting on index page merges. <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44911639"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT NAME, COMMENT FROM INFORMATION_SCHEMA.INNODB_METRICS WHERE NAME like '%index_page_merge%'; +-----------------------------+----------------------------------------+ | NAME | COMMENT | +-----------------------------+----------------------------------------+ | index_page_merge_attempts | Number of index page merge attempts | | index_page_merge_successful | Number of successful index page merges | +-----------------------------+----------------------------------------+</code></pre> </div> When lowering the <code class="literal"> MERGE_THRESHOLD </code> value, the objectives are: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> A smaller number of page merge attempts and successful page merges </li> <li class="listitem"> A similar number of page merge attempts and successful page merges </li> </ul> </div> A <code class="literal"> MERGE_THRESHOLD </code> setting that is too small could result in large data files due to an excessive amount of empty page space. For information about using <a class="link" href="information-schema-innodb-metrics-table.html" title="28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table"> <code class="literal"> INNODB_METRICS </code> </a> counters, see <a class="xref" href="innodb-information-schema-metrics-table.html" title="17.15.6 InnoDB INFORMATION_SCHEMA Metrics Table"> Section 17.15.6, “InnoDB INFORMATION_SCHEMA Metrics Table” </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/federated-description.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="federated-description"> </a> 18.8.1 FEDERATED Storage Engine Overview </h3> </div> </div> </div> When you create a table using one of the standard storage engines (such as <code class="literal"> MyISAM </code> , <code class="literal"> CSV </code> or <code class="literal"> InnoDB </code> ), the table consists of the table definition and the associated data. When you create a <code class="literal"> FEDERATED </code> table, the table definition is the same, but the physical storage of the data is handled on a remote server. A <code class="literal"> FEDERATED </code> table consists of two elements: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> A remote server with a database table, which in turn consists of the table definition (stored in the MySQL data dictionary) and the associated table. The table type of the remote table may be any type supported by the remote <code class="literal"> mysqld </code> server, including <code class="literal"> MyISAM </code> or <code class="literal"> InnoDB </code> . </li> <li class="listitem"> A local server with a database table, where the table definition matches that of the corresponding table on the remote server. The table definition is stored in the data dictionary. There is no data file on the local server. Instead, the table definition includes a connection string that points to the remote table. </li> </ul> </div> When executing queries and statements on a <code class="literal"> FEDERATED </code> table on the local server, the operations that would normally insert, update or delete information from a local data file are instead sent to the remote server for execution, where they update the data file on the remote server or return matching rows from the remote server. The basic structure of a <code class="literal"> FEDERATED </code> table setup is shown in <a class="xref" href="federated-description.html#figure-se-federated-structure" title="Figure 18.2 FEDERATED Table Structure"> Figure 18.2, “FEDERATED Table Structure” </a> . <div class="figure"> <a name="figure-se-federated-structure"> </a> Figure 18.2 FEDERATED Table Structure <div class="figure-contents"> <div class="mediaobject"> <img alt="Content is described in the surrounding text." src="images/se-federated-structure.png" style="width: 100%; max-width: 384px;"/> </div> </div> </div> When a client issues an SQL statement that refers to a <code class="literal"> FEDERATED </code> table, the flow of information between the local server (where the SQL statement is executed) and the remote server (where the data is physically stored) is as follows: <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> The storage engine looks through each column that the <code class="literal"> FEDERATED </code> table has and constructs an appropriate SQL statement that refers to the remote table. </li> <li class="listitem"> The statement is sent to the remote server using the MySQL client API. </li> <li class="listitem"> The remote server processes the statement and the local server retrieves any result that the statement produces (an affected-rows count or a result set). </li> <li class="listitem"> If the statement produces a result set, each column is converted to internal storage engine format that the <code class="literal"> FEDERATED </code> engine expects and can use to display the result to the client that issued the original statement. </li> </ol> </div> The local server communicates with the remote server using MySQL client C API functions. It invokes <a class="ulink" href="/doc/c-api/8.4/en/mysql-real-query.html" target="_top"> <code class="literal"> mysql_real_query() </code> </a> to send the statement. To read a result set, it uses <a class="ulink" href="/doc/c-api/8.4/en/mysql-store-result.html" target="_top"> <code class="literal"> mysql_store_result() </code> </a> and fetches rows one at a time using <a class="ulink" href="/doc/c-api/8.4/en/mysql-fetch-row.html" target="_top"> <code class="literal"> mysql_fetch_row() </code> </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-dict-obj-info.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysql-cluster-ndbinfo-dict-obj-info"> </a> 25.6.17.25 The ndbinfo dict_obj_info Table </h4> </div> </div> </div> <a class="indexterm" name="idm46045089672720"> </a> The <code class="literal"> dict_obj_info </code> table provides information about <code class="literal"> NDB </code> data dictionary ( <a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbdict.html" target="_top"> <code class="literal"> DICT </code> </a> ) objects such as tables and indexes. (The <a class="link" href="mysql-cluster-ndbinfo-dict-obj-types.html" title="25.6.17.27 The ndbinfo dict_obj_types Table"> <code class="literal"> dict_obj_types </code> </a> table can be queried for a list of all the types.) This information includes the object's type, state, parent object (if any), and fully qualified name. The <code class="literal"> dict_obj_info </code> table contains the following columns: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> type </code> Type of <a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbdict.html" target="_top"> <code class="literal"> DICT </code> </a> object; join on <a class="link" href="mysql-cluster-ndbinfo-dict-obj-types.html" title="25.6.17.27 The ndbinfo dict_obj_types Table"> <code class="literal"> dict_obj_types </code> </a> to obtain the name </li> <li class="listitem"> <code class="literal"> id </code> Object identifier; for Disk Data undo log files and data files, this is the same as the value shown in the <code class="literal"> LOGFILE_GROUP_NUMBER </code> column of the Information Schema <a class="link" href="information-schema-files-table.html" title="28.3.15 The INFORMATION_SCHEMA FILES Table"> <code class="literal"> FILES </code> </a> table; for undo log files, it also the same as the value shown for the <code class="literal"> log_id </code> column in the <code class="literal"> ndbinfo </code> <a class="link" href="mysql-cluster-ndbinfo-logbuffers.html" title="25.6.17.43 The ndbinfo logbuffers Table"> <code class="literal"> logbuffers </code> </a> and <a class="link" href="mysql-cluster-ndbinfo-logspaces.html" title="25.6.17.44 The ndbinfo logspaces Table"> <code class="literal"> logspaces </code> </a> tables </li> <li class="listitem"> <code class="literal"> version </code> Object version </li> <li class="listitem"> <code class="literal"> state </code> Object state; see <a class="ulink" href="/doc/ndbapi/en/ndb-object.html#ndb-object-state" target="_top"> Object::State </a> for values and descriptions. </li> <li class="listitem"> <code class="literal"> parent_obj_type </code> Parent object's type (a <code class="literal"> dict_obj_types </code> type ID); 0 indicates that the object has no parent </li> <li class="listitem"> <code class="literal"> parent_obj_id </code> Parent object ID (such as a base table); 0 indicates that the object has no parent </li> <li class="listitem"> <code class="literal"> fq_name </code> Fully qualified object name; for a table, this has the form <code class="literal"> <code> database_name </code> /def/ <code> table_name </code> </code> , for a primary key, the form is <code class="literal"> sys/def/ <code> table_id </code> /PRIMARY </code> , and for a unique key it is <code class="literal"> sys/def/ <code> table_id </code> / <code> uk_name </code> $unique </code> </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-ft-config-table.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="information-schema-innodb-ft-config-table"> </a> 28.4.15 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table </h3> </div> </div> </div> <a class="indexterm" name="idm46045076930576"> </a> The <a class="link" href="information-schema-innodb-ft-config-table.html" title="28.4.15 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table"> <code class="literal"> INNODB_FT_CONFIG </code> </a> table provides metadata about the <code class="literal"> FULLTEXT </code> index and associated processing for an <code class="literal"> InnoDB </code> table. This table is empty initially. Before querying it, set the value of the <a class="link" href="innodb-parameters.html#sysvar_innodb_ft_aux_table"> <code class="literal"> innodb_ft_aux_table </code> </a> system variable to the name (including the database name) of the table that contains the <code class="literal"> FULLTEXT </code> index (for example, <code class="literal"> test/articles </code> ). For related usage information and examples, see <a class="xref" href="innodb-information-schema-fulltext_index-tables.html" title="17.15.4 InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables"> Section 17.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables” </a> . The <a class="link" href="information-schema-innodb-ft-config-table.html" title="28.4.15 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table"> <code class="literal"> INNODB_FT_CONFIG </code> </a> table has these columns: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> KEY </code> The name designating an item of metadata for an <code class="literal"> InnoDB </code> table containing a <code class="literal"> FULLTEXT </code> index. The values for this column might change, depending on the needs for performance tuning and debugging for <code class="literal"> InnoDB </code> full-text processing. The key names and their meanings include: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <code class="literal"> optimize_checkpoint_limit </code> : The number of seconds after which an <a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement"> <code class="literal"> OPTIMIZE TABLE </code> </a> run stops. </li> <li class="listitem"> <code class="literal"> synced_doc_id </code> : The next <code class="literal"> DOC_ID </code> to be issued. </li> <li class="listitem"> <code class="literal"> stopword_table_name </code> : The <code> database/table </code> name for a user-defined stopword table. The <code class="literal"> VALUE </code> column is empty if there is no user-defined stopword table. </li> <li class="listitem"> <code class="literal"> use_stopword </code> : Indicates whether a stopword table is used, which is defined when the <code class="literal"> FULLTEXT </code> index is created. </li> </ul> </div> </li> <li class="listitem"> <code class="literal"> VALUE </code> The value associated with the corresponding <code class="literal"> KEY </code> column, reflecting some limit or current value for an aspect of a <code class="literal"> FULLTEXT </code> index for an <code class="literal"> InnoDB </code> table. </li> </ul> </div> <h4> <a name="idm46045076899952"> </a> Example </h4> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa71628088"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_FT_CONFIG; +---------------------------+-------------------+ | KEY | VALUE | +---------------------------+-------------------+ | optimize_checkpoint_limit | 180 | | synced_doc_id | 0 | | stopword_table_name | test/my_stopwords | | use_stopword | 1 | +---------------------------+-------------------+</code></pre> </div> <h4> <a name="idm46045076897200"> </a> Notes </h4> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> This table is intended only for internal configuration. It is not intended for statistical information purposes. </li> <li class="listitem"> You must have the <a class="link" href="privileges-provided.html#priv_process"> <code class="literal"> PROCESS </code> </a> privilege to query this table. </li> <li class="listitem"> Use the <code class="literal"> INFORMATION_SCHEMA </code> <a class="link" href="information-schema-columns-table.html" title="28.3.8 The INFORMATION_SCHEMA COLUMNS Table"> <code class="literal"> COLUMNS </code> </a> table or the <a class="link" href="show-columns.html" title="15.7.7.6 SHOW COLUMNS Statement"> <code class="literal"> SHOW COLUMNS </code> </a> statement to view additional information about the columns of this table, including data types and default values. </li> <li class="listitem"> For more information about <code class="literal"> InnoDB </code> <code class="literal"> FULLTEXT </code> search, see <a class="xref" href="innodb-fulltext-index.html" title="17.6.2.4 InnoDB Full-Text Indexes"> Section 17.6.2.4, “InnoDB Full-Text Indexes” </a> , and <a class="xref" href="fulltext-search.html" title="14.9 Full-Text Search Functions"> Section 14.9, “Full-Text Search Functions” </a> . </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/thread-pool-elements.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="thread-pool-elements"> </a> 7.6.3.1 Thread Pool Elements </h4> </div> </div> </div> <a class="indexterm" name="idm46045256857264"> </a> MySQL Enterprise Thread Pool comprises these elements: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> A plugin library file implements a plugin for the thread pool code as well as several associated monitoring tables that provide information about thread pool operation: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> In MySQL 8.4, the monitoring tables are Performance Schema tables; see <a class="xref" href="performance-schema-thread-pool-tables.html" title="29.12.16 Performance Schema Thread Pool Tables"> Section 29.12.16, “Performance Schema Thread Pool Tables” </a> . </li> <li class="listitem"> In older versions of MySQL, the monitoring tables were <code class="literal"> INFORMATION_SCHEMA </code> tables (see <a class="xref" href="thread-pool-information-schema-tables.html" title="28.5 INFORMATION_SCHEMA Thread Pool Tables"> Section 28.5, “INFORMATION_SCHEMA Thread Pool Tables” </a> ). The <code class="literal"> INFORMATION_SCHEMA </code> tables are deprecated; expect them to be removed in a future version of MySQL. Applications should transition away from the <code class="literal"> INFORMATION_SCHEMA </code> tables to the Performance Schema tables. For example, if an application uses this query: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa36939135"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SELECT * FROM INFORMATION_SCHEMA.TP_THREAD_STATE;</code></pre> </div> The application should use this query instead: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa66787753"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SELECT * FROM performance_schema.tp_thread_state;</code></pre> </div> </li> </ul> </div> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> If you do not load all the monitoring tables, some or all MySQL Enterprise Monitor thread pool graphs may be empty. </div> For a detailed description of how the thread pool works, see <a class="xref" href="thread-pool-operation.html" title="7.6.3.3 Thread Pool Operation"> Section 7.6.3.3, “Thread Pool Operation” </a> . </li> <li class="listitem"> Several system variables are related to the thread pool. The <a class="link" href="server-system-variables.html#sysvar_thread_handling"> <code class="literal"> thread_handling </code> </a> system variable has a value of <code class="literal"> loaded-dynamically </code> when the server successfully loads the thread pool plugin. The other related system variables are implemented by the thread pool plugin and are not available unless it is enabled. For information about using these variables, see <a class="xref" href="thread-pool-operation.html" title="7.6.3.3 Thread Pool Operation"> Section 7.6.3.3, “Thread Pool Operation” </a> , and <a class="xref" href="thread-pool-tuning.html" title="7.6.3.4 Thread Pool Tuning"> Section 7.6.3.4, “Thread Pool Tuning” </a> . </li> <li class="listitem"> The Performance Schema has instruments that expose information about the thread pool and may be used to investigate operational performance. To identify them, use this query: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63151090"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SELECT * FROM performance_schema.setup_instruments WHERE NAME LIKE '%thread_pool%';</code></pre> </div> For more information, see <a class="xref" href="performance-schema.html" title="Chapter 29 MySQL Performance Schema"> Chapter 29, MySQL Performance Schema </a> . </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/mysqlbinlog-hexdump.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysqlbinlog-hexdump"> </a> 6.6.9.1 mysqlbinlog Hex Dump Format </h4> </div> </div> </div> The <a class="link" href="mysqlbinlog.html#option_mysqlbinlog_hexdump"> <code class="option"> --hexdump </code> </a> option causes <a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files"> mysqlbinlog </a> to produce a hex dump of the binary log contents: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa17215586"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-terminal">mysqlbinlog --hexdump source-bin.000001</code></pre> </div> The hex output consists of comment lines beginning with <code class="literal"> # </code> , so the output might look like this for the preceding command: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa96387263"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">/*!40019 SET @@SESSION.max_insert_delayed_threads=0*/; /*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/; # at 4 #051024 17:24:13 server id 1 end_log_pos 98 # Position Timestamp Type Master ID Size Master Pos Flags # 00000004 9d fc 5c 43 0f 01 00 00 00 5e 00 00 00 62 00 00 00 00 00 # 00000017 04 00 35 2e 30 2e 31 35 2d 64 65 62 75 67 2d 6c |..5.0.15.debug.l| # 00000027 6f 67 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |og..............| # 00000037 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| # 00000047 00 00 00 00 9d fc 5c 43 13 38 0d 00 08 00 12 00 |.......C.8......| # 00000057 04 04 04 04 12 00 00 4b 00 04 1a |.......K...| # Start: binlog v 4, server v 5.0.15-debug-log created 051024 17:24:13 # at startup ROLLBACK;</code></pre> </div> Hex dump output currently contains the elements in the following list. This format is subject to change. For more information about binary log format, see <a class="ulink" href="/doc/internals/en/binary-log.html" target="_top"> MySQL Internals: The Binary Log </a> . <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> Position </code> : The byte position within the log file. </li> <li class="listitem"> <code class="literal"> Timestamp </code> : The event timestamp. In the example shown, <code class="literal"> '9d fc 5c 43' </code> is the representation of <code class="literal"> '051024 17:24:13' </code> in hexadecimal. </li> <li class="listitem"> <code class="literal"> Type </code> : The event type code. </li> <li class="listitem"> <code class="literal"> Master ID </code> : The server ID of the replication source server that created the event. </li> <li class="listitem"> <code class="literal"> Size </code> : The size in bytes of the event. </li> <li class="listitem"> <code class="literal"> Master Pos </code> : The position of the next event in the original source's binary log file. </li> <li class="listitem"> <code class="literal"> Flags </code> : Event flag values. </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/innodb-deadlock-detection.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="innodb-deadlock-detection"> </a> 17.7.5.2 Deadlock Detection </h4> </div> </div> </div> <a class="indexterm" name="idm46045163763152"> </a> <a class="indexterm" name="idm46045163761664"> </a> <a class="indexterm" name="idm46045163760592"> </a> <a class="indexterm" name="idm46045163759104"> </a> <a class="indexterm" name="idm46045163757200"> </a> <a class="indexterm" name="idm46045163755712"> </a> When <a class="link" href="glossary.html#glos_deadlock_detection" title="deadlock detection"> deadlock detection </a> is enabled (the default), <code class="literal"> InnoDB </code> automatically detects transaction <a class="link" href="glossary.html#glos_deadlock" title="deadlock"> deadlocks </a> and rolls back a transaction or transactions to break the deadlock. <code class="literal"> InnoDB </code> tries to pick small transactions to roll back, where the size of a transaction is determined by the number of rows inserted, updated, or deleted. <code class="literal"> InnoDB </code> is aware of table locks if <code class="literal"> innodb_table_locks = 1 </code> (the default) and <a class="link" href="server-system-variables.html#sysvar_autocommit"> <code class="literal"> autocommit = 0 </code> </a> , and the MySQL layer above it knows about row-level locks. Otherwise, <code class="literal"> InnoDB </code> cannot detect deadlocks where a table lock set by a MySQL <a class="link" href="lock-tables.html" title="15.3.6 LOCK TABLES and UNLOCK TABLES Statements"> <code class="literal"> LOCK TABLES </code> </a> statement or a lock set by a storage engine other than <code class="literal"> InnoDB </code> is involved. Resolve these situations by setting the value of the <a class="link" href="innodb-parameters.html#sysvar_innodb_lock_wait_timeout"> <code class="literal"> innodb_lock_wait_timeout </code> </a> system variable. If the <code class="literal"> LATEST DETECTED DEADLOCK </code> section of <code class="literal"> InnoDB </code> Monitor output includes a message stating TOO DEEP OR LONG SEARCH IN THE LOCK TABLE WAITS-FOR GRAPH, WE WILL ROLL BACK FOLLOWING TRANSACTION , this indicates that the number of transactions on the wait-for list has reached a limit of 200. A wait-for list that exceeds 200 transactions is treated as a deadlock and the transaction attempting to check the wait-for list is rolled back. The same error may also occur if the locking thread must look at more than 1,000,000 locks owned by transactions on the wait-for list. For techniques to organize database operations to avoid deadlocks, see <a class="xref" href="innodb-deadlocks.html" title="17.7.5 Deadlocks in InnoDB"> Section 17.7.5, “Deadlocks in InnoDB” </a> . <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="innodb-disable-deadlock-detection"> </a> Disabling Deadlock Detection </h5> </div> </div> </div> On high concurrency systems, deadlock detection can cause a slowdown when numerous threads wait for the same lock. At times, it may be more efficient to disable deadlock detection and rely on the <a class="link" href="innodb-parameters.html#sysvar_innodb_lock_wait_timeout"> <code class="literal"> innodb_lock_wait_timeout </code> </a> setting for transaction rollback when a deadlock occurs. Deadlock detection can be disabled using the <a class="link" href="innodb-parameters.html#sysvar_innodb_deadlock_detect"> <code class="literal"> innodb_deadlock_detect </code> </a> variable. </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/innodb-online-ddl.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="innodb-online-ddl"> </a> 17.12 InnoDB and Online DDL </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <a href="innodb-online-ddl-operations.html"> 17.12.1 Online DDL Operations </a> </dt> <dt> <a href="innodb-online-ddl-performance.html"> 17.12.2 Online DDL Performance and Concurrency </a> </dt> <dt> <a href="innodb-online-ddl-space-requirements.html"> 17.12.3 Online DDL Space Requirements </a> </dt> <dt> <a href="online-ddl-memory-management.html"> 17.12.4 Online DDL Memory Management </a> </dt> <dt> <a href="online-ddl-parallel-thread-configuration.html"> 17.12.5 Configuring Parallel Threads for Online DDL Operations </a> </dt> <dt> <a href="innodb-online-ddl-single-multi.html"> 17.12.6 Simplifying DDL Statements with Online DDL </a> </dt> <dt> <a href="innodb-online-ddl-failure-conditions.html"> 17.12.7 Online DDL Failure Conditions </a> </dt> <dt> <a href="innodb-online-ddl-limitations.html"> 17.12.8 Online DDL Limitations </a> </dt> </dl> </div> <a class="indexterm" name="idm46045160573136"> </a> <a class="indexterm" name="idm46045160572064"> </a> The online DDL feature provides support for instant and in-place table alterations and concurrent DML. Benefits of this feature include: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> Improved responsiveness and availability in busy production environments, where making a table unavailable for minutes or hours is not practical. </li> <li class="listitem"> For in-place operations, the ability to adjust the balance between performance and concurrency during DDL operations using the <code class="literal"> LOCK </code> clause. See <a class="xref" href="innodb-online-ddl-performance.html#innodb-online-ddl-locking-options" title="The LOCK clause"> The LOCK clause </a> . </li> <li class="listitem"> Less disk space usage and I/O overhead than the table-copy method. </li> </ul> </div> Typically, you do not need to do anything special to enable online DDL. By default, MySQL performs the operation instantly or in place, as permitted, with as little locking as possible. You can control aspects of a DDL operation using the <code class="literal"> ALGORITHM </code> and <code class="literal"> LOCK </code> clauses of the <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> statement. These clauses are placed at the end of the statement, separated from the table and column specifications by commas. For example: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa61546769"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">ALTER TABLE tbl_name ADD PRIMARY KEY (column), ALGORITHM=INPLACE;</code></pre> </div> The <code class="literal"> LOCK </code> clause may be used for operations that are performed in place and is useful for fine-tuning the degree of concurrent access to the table during operations. Only <code class="literal"> LOCK=DEFAULT </code> is supported for operations that are performed instantly. The <code class="literal"> ALGORITHM </code> clause is primarily intended for performance comparisons and as a fallback to the older table-copying behavior in case you encounter any issues. For example: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> To avoid accidentally making the table unavailable for reads, writes, or both, during an in-place <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> operation, specify a clause on the <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> statement such as <code class="literal"> LOCK=NONE </code> (permit reads and writes) or <code class="literal"> LOCK=SHARED </code> (permit reads). The operation halts immediately if the requested level of concurrency is not available. </li> <li class="listitem"> To compare performance between algorithms, run a statement with <code class="literal"> ALGORITHM=INSTANT </code> , <code class="literal"> ALGORITHM=INPLACE </code> and <code class="literal"> ALGORITHM=COPY </code> . You can also run a statement with the <a class="link" href="server-system-variables.html#sysvar_old_alter_table"> <code class="literal"> old_alter_table </code> </a> configuration option enabled to force the use of <code class="literal"> ALGORITHM=COPY </code> . </li> <li class="listitem"> To avoid tying up the server with an <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE </code> </a> operation that copies the table, include <code class="literal"> ALGORITHM=INSTANT </code> or <code class="literal"> ALGORITHM=INPLACE </code> . The statement halts immediately if it cannot use the specified algorithm. </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/clone-plugin-compressed-data.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="clone-plugin-compressed-data"> </a> 7.6.7.6 Cloning Compressed Data </h4> </div> </div> </div> <a class="indexterm" name="idm46045255409888"> </a> Cloning of page-compressed data is supported. The following requirements apply when cloning remote data: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> The recipient file system must support sparse files and hole punching for hole punching to occur on the recipient. </li> <li class="listitem"> The donor and recipient file systems must have the same block size. If file system block sizes differ, an error similar to the following is reported: ERROR 3868 (HY000): Clone Configuration FS Block Size: Donor value: 114688 is different from Recipient value: 4096 . </li> </ul> </div> For information about the page compression feature, see <a class="xref" href="innodb-page-compression.html" title="17.9.2 InnoDB Page Compression"> Section 17.9.2, “InnoDB Page Compression” </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/apis-ruby-mysqlruby.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="apis-ruby-mysqlruby"> </a> 31.11.1 The MySQL/Ruby API </h3> </div> </div> </div> The MySQL/Ruby module provides access to MySQL databases using Ruby through <code class="literal"> libmysqlclient </code> . For information on installing the module, and the functions exposed, see <a class="ulink" href="http://tmtm.org/en/mysql/ruby/" target="_blank"> MySQL/Ruby </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/faqs-virtualization.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="faqs-virtualization"> </a> A.18 MySQL 8.4 FAQ: Virtualization Support </h2> </div> </div> </div> <a class="indexterm" name="idm46045054794736"> </a> <div class="qandaset"> <a name="idm46045054793280"> </a> <dl> <dt> A.18.1. <a href="faqs-virtualization.html#faq-virtualization-support"> Is MySQL supported on virtualized environments such as Oracle VM, VMWare, Docker, Microsoft Hyper-V, or others? </a> </dt> </dl> <table border="0" style="width: 100%;"> <colgroup> <col align="left" width="1%"/> <col/> </colgroup> <tbody> <tr class="question"> <td align="left" valign="top"> <a name="faq-virtualization-support"> </a> <a name="idm46045054792464"> </a> A.18.1. </td> <td align="left" valign="top"> Is MySQL supported on virtualized environments such as Oracle VM, VMWare, Docker, Microsoft Hyper-V, or others? </td> </tr> <tr class="answer"> <td align="left" valign="top"> </td> <td align="left" valign="top"> MySQL is supported on virtualized environments, but is certified only for <a class="ulink" href="http://www.oracle.com/technetwork/server-storage/vm/index.html" target="_blank"> Oracle VM </a> . Contact Oracle Support for more information. Be aware of potential problems when using virtualization software. The usual ones are related to performance, performance degradations, slowness, or unpredictability of disk, I/O, network, and memory. </td> </tr> </tbody> </table> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/reset.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="reset"> </a> 15.7.8.6 RESET Statement </h4> </div> </div> </div> <a class="indexterm" name="idm46045168375264"> </a> <a class="indexterm" name="idm46045168374176"> </a> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa39287278"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">RESET reset_option [, reset_option] ... reset_option: { BINARY LOGS AND GTIDS | REPLICA }</code></pre> </div> The <a class="link" href="reset.html" title="15.7.8.6 RESET Statement"> <code class="literal"> RESET </code> </a> statement is used to clear the state of various server operations. You must have the <a class="link" href="privileges-provided.html#priv_reload"> <code class="literal"> RELOAD </code> </a> privilege to execute <a class="link" href="reset.html" title="15.7.8.6 RESET Statement"> <code class="literal"> RESET </code> </a> . For information about the <a class="link" href="reset-persist.html" title="15.7.8.7 RESET PERSIST Statement"> <code class="literal"> RESET PERSIST </code> </a> statement that removes persisted global system variables, see <a class="xref" href="reset-persist.html" title="15.7.8.7 RESET PERSIST Statement"> Section 15.7.8.7, “RESET PERSIST Statement” </a> . <a class="link" href="reset.html" title="15.7.8.6 RESET Statement"> <code class="literal"> RESET </code> </a> acts as a stronger version of the <a class="link" href="flush.html" title="15.7.8.3 FLUSH Statement"> <code class="literal"> FLUSH </code> </a> statement. See <a class="xref" href="flush.html" title="15.7.8.3 FLUSH Statement"> Section 15.7.8.3, “FLUSH Statement” </a> . The <a class="link" href="reset.html" title="15.7.8.6 RESET Statement"> <code class="literal"> RESET </code> </a> statement causes an implicit commit. See <a class="xref" href="implicit-commit.html" title="15.3.3 Statements That Cause an Implicit Commit"> Section 15.3.3, “Statements That Cause an Implicit Commit” </a> . The following list describes the permitted <a class="link" href="reset.html" title="15.7.8.6 RESET Statement"> <code class="literal"> RESET </code> </a> statement <code> reset_option </code> values: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <a class="link" href="reset-binary-logs-and-gtids.html" title="15.4.1.2 RESET BINARY LOGS AND GTIDS Statement"> <code class="literal"> RESET BINARY LOGS AND GTIDS </code> </a> Deletes all binary logs listed in the index file, resets the binary log index file to be empty, and creates a new binary log file. </li> <li class="listitem"> <a class="link" href="reset-replica.html" title="15.4.2.3 RESET REPLICA Statement"> <code class="literal"> RESET REPLICA </code> </a> Makes the replica forget its replication position in the source binary logs. Also resets the relay log by deleting any existing relay log files and beginning a new one. </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/firewall-information-schema-tables.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="firewall-information-schema-tables"> </a> 28.7 INFORMATION_SCHEMA MySQL Enterprise Firewall Tables </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <a href="information-schema-firewall-table-reference.html"> 28.7.1 INFORMATION_SCHEMA Firewall Table Reference </a> </dt> <dt> <a href="information-schema-mysql-firewall-users-table.html"> 28.7.2 The INFORMATION_SCHEMA MYSQL_FIREWALL_USERS Table </a> </dt> <dt> <a href="information-schema-mysql-firewall-whitelist-table.html"> 28.7.3 The INFORMATION_SCHEMA MYSQL_FIREWALL_WHITELIST Table </a> </dt> </dl> </div> <a class="indexterm" name="idm46045075980752"> </a> The following sections describe the <code class="literal"> INFORMATION_SCHEMA </code> tables associated with MySQL Enterprise Firewall (see <a class="xref" href="firewall.html" title="8.4.7 MySQL Enterprise Firewall"> Section 8.4.7, “MySQL Enterprise Firewall” </a> ). They provide views into the firewall in-memory data cache. These tables are available only if the appropriate firewall plugins are enabled. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/linux-installation-juju.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="linux-installation-juju"> </a> 2.5.8 Installing MySQL on Linux with Juju </h3> </div> </div> </div> The Juju deployment framework supports easy installation and configuration of MySQL servers. For instructions, see <a class="ulink" href="https://jujucharms.com/mysql/" target="_blank"> https://jujucharms.com/mysql/ </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-buffer-pool-stats-table.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="information-schema-innodb-buffer-pool-stats-table"> </a> 28.4.4 The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table </h3> </div> </div> </div> <a class="indexterm" name="idm46045077425312"> </a> The <a class="link" href="information-schema-innodb-buffer-pool-stats-table.html" title="28.4.4 The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table"> <code class="literal"> INNODB_BUFFER_POOL_STATS </code> </a> table provides much of the same buffer pool information provided in <a class="link" href="show-engine.html" title="15.7.7.16 SHOW ENGINE Statement"> <code class="literal"> SHOW ENGINE INNODB STATUS </code> </a> output. Much of the same information may also be obtained using <code class="literal"> InnoDB </code> buffer pool <a class="link" href="server-status-variables.html" title="7.1.10 Server Status Variables"> server status variables </a> . The idea of making pages in the buffer pool “ young ” or “ not young ” refers to transferring them between the <a class="link" href="glossary.html#glos_sublist" title="sublist"> sublists </a> at the head and tail of the buffer pool data structure. Pages made “ young ” take longer to age out of the buffer pool, while pages made “ not young ” are moved much closer to the point of <a class="link" href="glossary.html#glos_eviction" title="eviction"> eviction </a> . For related usage information and examples, see <a class="xref" href="innodb-information-schema-buffer-pool-tables.html" title="17.15.5 InnoDB INFORMATION_SCHEMA Buffer Pool Tables"> Section 17.15.5, “InnoDB INFORMATION_SCHEMA Buffer Pool Tables” </a> . The <a class="link" href="information-schema-innodb-buffer-pool-stats-table.html" title="28.4.4 The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table"> <code class="literal"> INNODB_BUFFER_POOL_STATS </code> </a> table has these columns: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> POOL_ID </code> The buffer pool ID. This is an identifier to distinguish between multiple buffer pool instances. </li> <li class="listitem"> <code class="literal"> POOL_SIZE </code> The <code class="literal"> InnoDB </code> buffer pool size in pages. </li> <li class="listitem"> <code class="literal"> FREE_BUFFERS </code> The number of free pages in the <code class="literal"> InnoDB </code> buffer pool. </li> <li class="listitem"> <code class="literal"> DATABASE_PAGES </code> The number of pages in the <code class="literal"> InnoDB </code> buffer pool containing data. This number includes both dirty and clean pages. </li> <li class="listitem"> <code class="literal"> OLD_DATABASE_PAGES </code> The number of pages in the <code class="literal"> old </code> buffer pool sublist. </li> <li class="listitem"> <code class="literal"> MODIFIED_DATABASE_PAGES </code> The number of modified (dirty) database pages. </li> <li class="listitem"> <code class="literal"> PENDING_DECOMPRESS </code> The number of pages pending decompression. </li> <li class="listitem"> <code class="literal"> PENDING_READS </code> The number of pending reads. </li> <li class="listitem"> <code class="literal"> PENDING_FLUSH_LRU </code> The number of pages pending flush in the LRU. </li> <li class="listitem"> <code class="literal"> PENDING_FLUSH_LIST </code> The number of pages pending flush in the flush list. </li> <li class="listitem"> <code class="literal"> PAGES_MADE_YOUNG </code> The number of pages made young. </li> <li class="listitem"> <code class="literal"> PAGES_NOT_MADE_YOUNG </code> The number of pages not made young. </li> <li class="listitem"> <code class="literal"> PAGES_MADE_YOUNG_RATE </code> The number of pages made young per second (pages made young since the last printout / time elapsed). </li> <li class="listitem"> <code class="literal"> PAGES_MADE_NOT_YOUNG_RATE </code> The number of pages not made per second (pages not made young since the last printout / time elapsed). </li> <li class="listitem"> <code class="literal"> NUMBER_PAGES_READ </code> The number of pages read. </li> <li class="listitem"> <code class="literal"> NUMBER_PAGES_CREATED </code> The number of pages created. </li> <li class="listitem"> <code class="literal"> NUMBER_PAGES_WRITTEN </code> The number of pages written. </li> <li class="listitem"> <code class="literal"> PAGES_READ_RATE </code> The number of pages read per second (pages read since the last printout / time elapsed). </li> <li class="listitem"> <code class="literal"> PAGES_CREATE_RATE </code> The number of pages created per second (pages created since the last printout / time elapsed). </li> <li class="listitem"> <code class="literal"> PAGES_WRITTEN_RATE </code> The number of pages written per second (pages written since the last printout / time elapsed). </li> <li class="listitem"> <code class="literal"> NUMBER_PAGES_GET </code> The number of logical read requests. </li> <li class="listitem"> <code class="literal"> HIT_RATE </code> The buffer pool hit rate. </li> <li class="listitem"> <code class="literal"> YOUNG_MAKE_PER_THOUSAND_GETS </code> The number of pages made young per thousand gets. </li> <li class="listitem"> <code class="literal"> NOT_YOUNG_MAKE_PER_THOUSAND_GETS </code> The number of pages not made young per thousand gets. </li> <li class="listitem"> <code class="literal"> NUMBER_PAGES_READ_AHEAD </code> The number of pages read ahead. </li> <li class="listitem"> <code class="literal"> NUMBER_READ_AHEAD_EVICTED </code> The number of pages read into the <code class="literal"> InnoDB </code> buffer pool by the read-ahead background thread that were subsequently evicted without having been accessed by queries. </li> <li class="listitem"> <code class="literal"> READ_AHEAD_RATE </code> The read-ahead rate per second (pages read ahead since the last printout / time elapsed). </li> <li class="listitem"> <code class="literal"> READ_AHEAD_EVICTED_RATE </code> The number of read-ahead pages evicted without access per second (read-ahead pages not accessed since the last printout / time elapsed). </li> <li class="listitem"> <code class="literal"> LRU_IO_TOTAL </code> Total LRU I/O. </li> <li class="listitem"> <code class="literal"> LRU_IO_CURRENT </code> LRU I/O for the current interval. </li> <li class="listitem"> <code class="literal"> UNCOMPRESS_TOTAL </code> The total number of pages decompressed. </li> <li class="listitem"> <code class="literal"> UNCOMPRESS_CURRENT </code> The number of pages decompressed in the current interval. </li> </ul> </div> <h4> <a name="idm46045077346112"> </a> Example </h4> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75073322"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_BUFFER_POOL_STATS\G *************************** 1. row *************************** POOL_ID: 0 POOL_SIZE: 8192 FREE_BUFFERS: 1 DATABASE_PAGES: 8085 OLD_DATABASE_PAGES: 2964 MODIFIED_DATABASE_PAGES: 0 PENDING_DECOMPRESS: 0 PENDING_READS: 0 PENDING_FLUSH_LRU: 0 PENDING_FLUSH_LIST: 0 PAGES_MADE_YOUNG: 22821 PAGES_NOT_MADE_YOUNG: 3544303 PAGES_MADE_YOUNG_RATE: 357.62602199870594 PAGES_MADE_NOT_YOUNG_RATE: 0 NUMBER_PAGES_READ: 2389 NUMBER_PAGES_CREATED: 12385 NUMBER_PAGES_WRITTEN: 13111 PAGES_READ_RATE: 0 PAGES_CREATE_RATE: 0 PAGES_WRITTEN_RATE: 0 NUMBER_PAGES_GET: 33322210 HIT_RATE: 1000 YOUNG_MAKE_PER_THOUSAND_GETS: 18 NOT_YOUNG_MAKE_PER_THOUSAND_GETS: 0 NUMBER_PAGES_READ_AHEAD: 2024 NUMBER_READ_AHEAD_EVICTED: 0 READ_AHEAD_RATE: 0 READ_AHEAD_EVICTED_RATE: 0 LRU_IO_TOTAL: 0 LRU_IO_CURRENT: 0 UNCOMPRESS_TOTAL: 0 UNCOMPRESS_CURRENT: 0</code></pre> </div> <h4> <a name="idm46045077341184"> </a> Notes </h4> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> This table is useful primarily for expert-level performance monitoring, or when developing performance-related extensions for MySQL. </li> <li class="listitem"> You must have the <a class="link" href="privileges-provided.html#priv_process"> <code class="literal"> PROCESS </code> </a> privilege to query this table. </li> <li class="listitem"> Use the <code class="literal"> INFORMATION_SCHEMA </code> <a class="link" href="information-schema-columns-table.html" title="28.3.8 The INFORMATION_SCHEMA COLUMNS Table"> <code class="literal"> COLUMNS </code> </a> table or the <a class="link" href="show-columns.html" title="15.7.7.6 SHOW COLUMNS Statement"> <code class="literal"> SHOW COLUMNS </code> </a> statement to view additional information about the columns of this table, including data types and default values. </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/replication-administration-status.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="replication-administration-status"> </a> 19.1.7.1 Checking Replication Status </h4> </div> </div> </div> The most common task when managing a replication process is to ensure that replication is taking place and that there have been no errors between the replica and the source. The <a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement"> <code class="literal"> SHOW REPLICA STATUS </code> </a> statement, which you must execute on each replica, provides information about the configuration and status of the connection between the replica server and the source server. The MySQL Performance Schema contains replication tables that provide this information in a more accessible form. See <a class="xref" href="performance-schema-replication-tables.html" title="29.12.11 Performance Schema Replication Tables"> Section 29.12.11, “Performance Schema Replication Tables” </a> . The replication heartbeat information shown in the Performance Schema replication tables lets you check that the replication connection is active even if the source has not sent events to the replica recently. The source sends a heartbeat signal to a replica if there are no updates to, and no unsent events in, the binary log for a longer period than the heartbeat interval. The <code class="literal"> SOURCE_HEARTBEAT_PERIOD </code> setting on the source (set by <a class="link" href="change-replication-source-to.html" title="15.4.2.2 CHANGE REPLICATION SOURCE TO Statement"> <code class="literal"> CHANGE REPLICATION SOURCE TO </code> </a> ) specifies the frequency of the heartbeat, which defaults to half of the connection timeout interval for the replica (specified by the system variable <a class="link" href="replication-options-replica.html#sysvar_replica_net_timeout"> <code class="literal"> replica_net_timeout </code> </a> . The <a class="link" href="performance-schema-replication-connection-status-table.html" title="29.12.11.13 The replication_connection_status Table"> <code class="literal"> replication_connection_status </code> </a> Performance Schema table shows when the most recent heartbeat signal was received by a replica, and how many heartbeat signals it has received. You can use <a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement"> <code class="literal"> SHOW REPLICA STATUS </code> </a> to check on the status of an individual replica; this statement provides the information shown here: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa50743417"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SHOW REPLICA STATUS\G *************************** 1. row *************************** Replica_IO_State: Waiting for source to send event Source_Host: 127.0.0.1 Source_User: root Source_Port: 13000 Connect_Retry: 1 Source_Log_File: master-bin.000001 Read_Source_Log_Pos: 927 Relay_Log_File: slave-relay-bin.000002 Relay_Log_Pos: 1145 Relay_Source_Log_File: master-bin.000001 Replica_IO_Running: Yes Replica_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Source_Log_Pos: 927 Relay_Log_Space: 1355 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Source_SSL_Allowed: No Source_SSL_CA_File: Source_SSL_CA_Path: Source_SSL_Cert: Source_SSL_Cipher: Source_SSL_Key: Seconds_Behind_Source: 0 Source_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Source_Server_Id: 1 Source_UUID: 73f86016-978b-11ee-ade5-8d2a2a562feb Source_Info_File: mysql.slave_master_info SQL_Delay: 0 SQL_Remaining_Delay: NULL Replica_SQL_Running_State: Replica has read all relay log; waiting for more updates Source_Retry_Count: 10 Source_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: Source_SSL_Crl: Source_SSL_Crlpath: Retrieved_Gtid_Set: 73f86016-978b-11ee-ade5-8d2a2a562feb:1-3 Executed_Gtid_Set: 73f86016-978b-11ee-ade5-8d2a2a562feb:1-3 Auto_Position: 1 Replicate_Rewrite_DB: Channel_Name: Source_TLS_Version: Source_public_key_path: Get_Source_public_key: 0 Network_Namespace:</code></pre> </div> The key fields from the status report to examine are: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> Replica_IO_State </code> : The current status of the replica. See <a class="xref" href="replica-io-thread-states.html" title="10.14.5 Replication I/O (Receiver) Thread States"> Section 10.14.5, “Replication I/O (Receiver) Thread States” </a> , and <a class="xref" href="replica-sql-thread-states.html" title="10.14.6 Replication SQL Thread States"> Section 10.14.6, “Replication SQL Thread States” </a> , for more information. </li> <li class="listitem"> <code class="literal"> Replica_IO_Running </code> : Whether the I/O (receiver) thread for reading the source's binary log is running. Normally, you want this to be <code class="literal"> Yes </code> unless you have not yet started replication or have explicitly stopped it with <a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement"> <code class="literal"> STOP REPLICA </code> </a> . </li> <li class="listitem"> <code class="literal"> Replica_SQL_Running </code> : Whether the SQL thread for executing events in the relay log is running. As with the I/O thread, this should normally be <code class="literal"> Yes </code> . </li> <li class="listitem"> <code class="literal"> Last_IO_Error </code> , <code class="literal"> Last_SQL_Error </code> : The last errors registered by the I/O (receiver) and SQL (applier) threads when processing the relay log. Ideally these should be blank, indicating no errors. </li> <li class="listitem"> <code class="literal"> Seconds_Behind_Source </code> : The number of seconds that the replication SQL (applier) thread is behind processing the source binary log. A high number (or an increasing one) can indicate that the replica is unable to handle events from the source in a timely fashion. A value of 0 for <code class="literal"> Seconds_Behind_Source </code> can usually be interpreted as meaning that the replica has caught up with the source, but there are some cases where this is not strictly true. For example, this can occur if the network connection between source and replica is broken but the replication I/O (receiver) thread has not yet noticed this; that is, the time period set by <a class="link" href="replication-options-replica.html#sysvar_replica_net_timeout"> <code class="literal"> replica_net_timeout </code> </a> has not yet elapsed. It is also possible that transient values for <code class="literal"> Seconds_Behind_Source </code> may not reflect the situation accurately. When the replication SQL (applier) thread has caught up on I/O, <code class="literal"> Seconds_Behind_Source </code> displays 0; but when the replication I/O (receiver) thread is still queuing up a new event, <code class="literal"> Seconds_Behind_Source </code> may show a large value until the replication applier thread finishes executing the new event. This is especially likely when the events have old timestamps; in such cases, if you execute <a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement"> <code class="literal"> SHOW REPLICA STATUS </code> </a> several times in a relatively short period, you may see this value change back and forth repeatedly between 0 and a relatively large value. </li> </ul> </div> Several pairs of fields provide information about the progress of the replica in reading events from the source binary log and processing them in the relay log: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> ( <code class="literal"> Master_Log_file </code> , <code class="literal"> Read_Master_Log_Pos </code> ): Coordinates in the source binary log indicating how far the replication I/O (receiver) thread has read events from that log. </li> <li class="listitem"> ( <code class="literal"> Relay_Master_Log_File </code> , <code class="literal"> Exec_Master_Log_Pos </code> ): Coordinates in the source binary log indicating how far the replication SQL (applier) thread has executed events received from that log. </li> <li class="listitem"> ( <code class="literal"> Relay_Log_File </code> , <code class="literal"> Relay_Log_Pos </code> ): Coordinates in the replica relay log indicating how far the replication SQL (applier) thread has executed the relay log. These correspond to the preceding coordinates, but are expressed in replica relay log coordinates rather than source binary log coordinates. </li> </ul> </div> On the source, you can check the status of connected replicas using <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> to examine the list of running processes. Replica connections have <code class="literal"> Binlog Dump </code> in the <code class="literal"> Command </code> field: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa2643694"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SHOW PROCESSLIST \G; *************************** 4. row *************************** Id: 10 User: root Host: replica1:58371 db: NULL Command: Binlog Dump Time: 777 State: Has sent all binlog to slave; waiting for binlog to be updated Info: NULL</code></pre> </div> Because it is the replica that drives the replication process, very little information is available in this report. For replicas that were started with the <a class="link" href="replication-options-replica.html#sysvar_report_host"> <code class="option"> --report-host </code> </a> option and are connected to the source, the <a class="link" href="show-replicas.html" title="15.7.7.36 SHOW REPLICAS Statement"> <code class="literal"> SHOW REPLICAS </code> </a> statement on the source shows basic information about the replicas. The output includes the ID of the replica server, the value of the <a class="link" href="replication-options-replica.html#sysvar_report_host"> <code class="option"> --report-host </code> </a> option, the connecting port, and source ID: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa35317527"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SHOW REPLICAS; +-----------+----------+------+-------------------+-----------+ | Server_id | Host | Port | Rpl_recovery_rank | Source_id | +-----------+----------+------+-------------------+-----------+ | 10 | replica1 | 3306 | 0 | 1 | +-----------+----------+------+-------------------+-----------+ 1 row in set (0.00 sec)</code></pre> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/replication-privilege-checks-recover.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="replication-privilege-checks-recover"> </a> 19.3.3.3 Recovering From Failed Replication Privilege Checks </h4> </div> </div> </div> If a privilege check against the <code class="literal"> PRIVILEGE_CHECKS_USER </code> account fails, the transaction is not executed and replication stops for the channel. Details of the error and the last applied transaction are recorded in the Performance Schema <a class="link" href="performance-schema-replication-applier-status-by-worker-table.html" title="29.12.11.7 The replication_applier_status_by_worker Table"> <code class="literal"> replication_applier_status_by_worker </code> </a> table. Follow this procedure to recover from the error: <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> Identify the replicated event that caused the error and verify whether or not the event is expected and from a trusted source. You can use <a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files"> mysqlbinlog </a> to retrieve and display the events that were logged around the time of the error. For instructions to do this, see <a class="xref" href="point-in-time-recovery.html" title="9.5 Point-in-Time (Incremental) Recovery"> Section 9.5, “Point-in-Time (Incremental) Recovery” </a> . </li> <li class="listitem"> If the replicated event is not expected or is not from a known and trusted source, investigate the cause. If you can identify why the event took place and there are no security considerations, proceed to fix the error as described below. </li> <li class="listitem"> If the <code class="literal"> PRIVILEGE_CHECKS_USER </code> account should have been permitted to execute the transaction, but has been misconfigured, grant the missing privileges to the account, use a <a class="link" href="flush.html#flush-privileges"> <code class="literal"> FLUSH PRIVILEGES </code> </a> statement or execute a <a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program"> mysqladmin flush-privileges </a> or <a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program"> mysqladmin reload </a> command to reload the grant tables, then restart replication for the channel. </li> <li class="listitem"> If the transaction needs to be executed and you have verified that it is trusted, but the <code class="literal"> PRIVILEGE_CHECKS_USER </code> account should not have this privilege normally, you can grant the required privilege to the <code class="literal"> PRIVILEGE_CHECKS_USER </code> account temporarily. After the replicated event has been applied, remove the privilege from the account, and take any necessary steps to ensure the event does not recur if it is avoidable. </li> <li class="listitem"> If the transaction is an administrative action that should only have taken place on the source and not on the replica, or should only have taken place on a single replication group member, skip the transaction on the server or servers where it stopped replication, then issue <a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement"> <code class="literal"> START REPLICA </code> </a> to restart replication on the channel. To avoid the situation in future, you could issue such administrative statements with <code class="literal"> SET sql_log_bin = 0 </code> before them and <code class="literal"> SET sql_log_bin = 1 </code> after them, so that they are not logged on the source. </li> <li class="listitem"> If the transaction is a DDL or DML statement that should not have taken place on either the source or the replica, skip the transaction on the server or servers where it stopped replication, undo the transaction manually on the server where it originally took place, then issue <a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement"> <code class="literal"> START REPLICA </code> </a> to restart replication. </li> </ol> </div> To skip a transaction, if GTIDs are in use, commit an empty transaction that has the GTID of the failing transaction, for example: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa35036198"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SET GTID_NEXT='aaa-bbb-ccc-ddd:N'; BEGIN; COMMIT; SET GTID_NEXT='AUTOMATIC';</code></pre> </div> If GTIDs are not in use, issue a <code class="literal"> SET GLOBAL sql_replica_skip_counter </code> statement to skip the event. For instructions to use this alternative method and more details about skipping transactions, see <a class="xref" href="replication-administration-skip.html" title="19.1.7.3 Skipping Transactions"> Section 19.1.7.3, “Skipping Transactions” </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/group-replication-single-primary-mode.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="group-replication-single-primary-mode"> </a> 20.1.3.1 Single-Primary Mode </h4> </div> </div> </div> <a class="indexterm" name="idm46045134489696"> </a> <a class="indexterm" name="idm46045134488208"> </a> In single-primary mode ( <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_single_primary_mode"> <code class="literal"> group_replication_single_primary_mode=ON </code> </a> ) the group has a single primary server that is set to read/write mode. All the other members in the group are set to read-only mode (with <a class="link" href="server-system-variables.html#sysvar_super_read_only"> <code class="literal"> super_read_only=ON </code> </a> ). The primary typically bootstraps the entire group. All other servers that join the group learn about the primary server and are automatically set to read-only mode. In single-primary mode, Group Replication enforces that only a single server writes to the group, so compared to multi-primary mode, consistency checking can be less strict and DDL statements do not need to be handled with any extra care. The option <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_enforce_update_everywhere_checks"> <code class="literal"> group_replication_enforce_update_everywhere_checks </code> </a> enables or disables strict consistency checks for a group. When deploying in single-primary mode, or changing the group to single-primary mode, this system variable must be set to <code class="literal"> OFF </code> . The member that is designated as the primary server can change in the following ways: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> If the existing primary leaves the group, whether voluntarily or unexpectedly, a new primary is elected automatically. </li> <li class="listitem"> You can appoint a specific member as the new primary using the <a class="link" href="group-replication-functions-for-new-primary.html#function_group-replication-set-as-primary"> <code class="literal"> group_replication_set_as_primary() </code> </a> function. </li> <li class="listitem"> If you use the <a class="link" href="group-replication-functions-for-mode.html#function_group-replication-switch-to-single-primary-mode"> <code class="literal"> group_replication_switch_to_single_primary_mode() </code> </a> function to change a group that was running in multi-primary mode to run in single-primary mode, a new primary is elected automatically, or you can appoint the new primary by specifying it with the function. </li> </ul> </div> When a new primary server is elected (automatically or manually), it is automatically set to read/write, and the other group members remain as secondaries, and as such, read-only. The following diagram shows this process: <div class="figure"> <a name="group-replication-primary-election-diagram"> </a> Figure 20.4 New Primary Election <div class="figure-contents"> <div class="mediaobject"> <img alt="Five server instances, S1, S2, S3, S4, and S5, are deployed as an interconnected group. Server S1 is the primary. Write clients are communicating with server S1, and a read client is communicating with server S4. Server S1 then fails, breaking communication with the write clients. Server S2 then takes over as the new primary, and the write clients now communicate with server S2." src="images/single-primary-election.png" style="width: 100%; max-width: 899px;"/> </div> </div> </div> When a new primary is chosen, it might have a backlog of changes that had been applied on the old primary but have not yet been applied on the new one. In this case, until the new primary catches up with the old one, read/write transactions might result in conflicts and be rolled back, and read-only transactions might result in stale reads. The Group Replication flow control mechanism minimizes the difference between fast and slow members, and so reduces the chances of this happening if it is activated and properly tuned. For more information, see <a class="xref" href="group-replication-flow-control.html" title="20.7.2 Flow Control"> Section 20.7.2, “Flow Control” </a> . You can also use the <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_consistency"> <code class="literal"> group_replication_consistency </code> </a> system variable to set the group's level of transaction consistency to prevent this issue. Setting this variable to <code class="literal"> BEFORE_ON_PRIMARY_FAILOVER </code> (the default) or any higher consistency level holds new transactions on a newly elected primary until the backlog has been applied. For more information on transaction consistency, see <a class="xref" href="group-replication-consistency-guarantees.html" title="20.5.3 Transaction Consistency Guarantees"> Section 20.5.3, “Transaction Consistency Guarantees” </a> . If flow control and transaction consistency guarantees are not used for a group, it is a good practice to wait for the new primary to apply its replication-related relay log before re-routing client applications to it. <div class="section"> <div class="titlepage"> <div> <div> <h5 class="title"> <a name="group-replication-primary-election"> </a> 20.1.3.1.1 Primary Election Algorithm </h5> </div> </div> </div> The automatic primary member election process involves each member looking at the new view of the group, ordering the potential new primary members, and choosing the member that qualifies as the most suitable. Each member makes its own decision locally, following the primary election algorithm in its MySQL Server release. Because all members must reach the same decision, members adapt their primary election algorithm if other group members are running lower MySQL Server versions, so that they have the same behavior as the member with the lowest MySQL Server version in the group. The factors considered by members when electing a primary, in order, are as follows: <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> The first factor considered is which member or members are running the lowest MySQL Server version. All group members are first ordered by the patch version of their release. </li> <li class="listitem"> If more than one member is running the lowest MySQL Server version, the second factor considered is the member weight of each of those members, as specified by the <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_member_weight"> <code class="literal"> group_replication_member_weight </code> </a> system variable on the member. The <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_member_weight"> <code class="literal"> group_replication_member_weight </code> </a> system variable specifies a number in the range 0-100. All members default to a weight of 50, so set a weight below this to lower their ordering, and a weight above it to increase their ordering. You can use this weighting function to prioritize the use of better hardware or to ensure failover to a specific member during scheduled maintenance of the primary. </li> <li class="listitem"> If more than one member is running the lowest MySQL Server version, and more than one of those members has the highest member weight (or member weighting is being ignored), the third factor considered is the lexicographical order of the generated server UUIDs of each member, as specified by the <a class="link" href="replication-options.html#sysvar_server_uuid"> <code class="literal"> server_uuid </code> </a> system variable. The member with the lowest server UUID is chosen as the primary. This factor acts as a guaranteed and predictable tie-breaker so that all group members reach the same decision if it cannot be determined by any important factors. </li> </ol> </div> </div> <div class="section"> <div class="titlepage"> <div> <div> <h5 class="title"> <a name="group-replication-find-primary"> </a> 20.1.3.1.2 Finding the Primary </h5> </div> </div> </div> <a class="indexterm" name="idm46045134447520"> </a> To find out which server is currently the primary when deployed in single-primary mode, use the <code class="literal"> MEMBER_ROLE </code> column in the <a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table"> <code class="literal"> performance_schema.replication_group_members </code> </a> table. For example: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa42339057"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT MEMBER_HOST, MEMBER_ROLE FROM performance_schema.replication_group_members; +-------------------------+-------------+ | MEMBER_HOST | MEMBER_ROLE | +-------------------------+-------------+ | remote1.example.com | PRIMARY | | remote2.example.com | SECONDARY | | remote3.example.com | SECONDARY | +-------------------------+-------------+</code></pre> </div> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/fulltext-query-expansion.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="fulltext-query-expansion"> </a> 14.9.3 Full-Text Searches with Query Expansion </h3> </div> </div> </div> <a class="indexterm" name="idm46045201620208"> </a> <a class="indexterm" name="idm46045201619136"> </a> Full-text search supports query expansion (and in particular, its variant “ blind query expansion ” ). This is generally useful when a search phrase is too short, which often means that the user is relying on implied knowledge that the full-text search engine lacks. For example, a user searching for “ database ” may really mean that “ MySQL ” , “ Oracle ” , “ DB2 ” , and “ RDBMS ” all are phrases that should match “ databases ” and should be returned, too. This is implied knowledge. Blind query expansion (also known as automatic relevance feedback) is enabled by adding <code class="literal"> WITH QUERY EXPANSION </code> or <code class="literal"> IN NATURAL LANGUAGE MODE WITH QUERY EXPANSION </code> following the search phrase. It works by performing the search twice, where the search phrase for the second search is the original search phrase concatenated with the few most highly relevant documents from the first search. Thus, if one of these documents contains the word “ databases ” and the word “ MySQL ” , the second search finds the documents that contain the word “ MySQL ” even if they do not contain the word “ database ” . The following example shows this difference: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa9375064"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT * FROM articles WHERE MATCH (title,body) AGAINST ('database' IN NATURAL LANGUAGE MODE); +----+-------------------+------------------------------------------+ | id | title | body | +----+-------------------+------------------------------------------+ | 1 | MySQL Tutorial | DBMS stands for DataBase ... | | 5 | MySQL vs. YourSQL | In the following database comparison ... | +----+-------------------+------------------------------------------+ 2 rows in set (0.00 sec) mysql> SELECT * FROM articles WHERE MATCH (title,body) AGAINST ('database' WITH QUERY EXPANSION); +----+-----------------------+------------------------------------------+ | id | title | body | +----+-----------------------+------------------------------------------+ | 5 | MySQL vs. YourSQL | In the following database comparison ... | | 1 | MySQL Tutorial | DBMS stands for DataBase ... | | 3 | Optimizing MySQL | In this tutorial we show ... | | 6 | MySQL Security | When configured properly, MySQL ... | | 2 | How To Use MySQL Well | After you went through a ... | | 4 | 1001 MySQL Tricks | 1. Never run mysqld as root. 2. ... | +----+-----------------------+------------------------------------------+ 6 rows in set (0.00 sec)</code></pre> </div> Another example could be searching for books by Georges Simenon about Maigret, when a user is not sure how to spell “ Maigret ” . A search for “ Megre and the reluctant witnesses ” finds only “ Maigret and the Reluctant Witnesses ” without query expansion. A search with query expansion finds all books with the word “ Maigret ” on the second pass. <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> Because blind query expansion tends to increase noise significantly by returning nonrelevant documents, use it only when a search phrase is short. </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-rolling-restart.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="mysql-cluster-rolling-restart"> </a> 25.6.5 Performing a Rolling Restart of an NDB Cluster </h3> </div> </div> </div> <a class="indexterm" name="idm46045092605824"> </a> <a class="indexterm" name="idm46045092604336"> </a> <a class="indexterm" name="idm46045092603232"> </a> <a class="indexterm" name="idm46045092601744"> </a> <a class="indexterm" name="idm46045092600256"> </a> This section discusses how to perform a rolling restart of an NDB Cluster installation, so called because it involves stopping and starting (or restarting) each node in turn, so that the cluster itself remains operational. This is often done as part of a rolling upgrade or rolling downgrade , where high availability of the cluster is mandatory and no downtime of the cluster as a whole is permissible. Where we refer to upgrades, the information provided here also generally applies to downgrades as well. There are a number of reasons why a rolling restart might be desirable. These are described in the next few paragraphs. Configuration change. <a class="indexterm" name="idm46045092594960"> </a> To make a change in the cluster's configuration, such as adding an SQL node to the cluster, or setting a configuration parameter to a new value. NDB Cluster software upgrade or downgrade. To upgrade the cluster to a newer version of the NDB Cluster software (or to downgrade it to an older version). This is usually referred to as a “ rolling upgrade ” (or “ rolling downgrade ” , when reverting to an older version of NDB Cluster). Change on node host. To make changes in the hardware or operating system on which one or more NDB Cluster node processes are running. System reset (cluster reset). <a class="indexterm" name="idm46045092588384"> </a> To reset the cluster because it has reached an undesirable state. In such cases it is often desirable to reload the data and metadata of one or more data nodes. This can be done in any of three ways: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> Start each data node process ( <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> ndbd </a> or possibly <a class="link" href="mysql-cluster-programs-ndbmtd.html" title="25.5.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)"> ndbmtd </a> ) with the <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_initial"> <code class="option"> --initial </code> </a> option, which forces the data node to clear its file system and to reload all NDB Cluster data and metadata from the other data nodes. This also forces the removal of all Disk Data objects and files associated with those objects. </li> <li class="listitem"> Create a backup using the <a class="link" href="mysql-cluster-programs-ndb-mgm.html" title="25.5.5 ndb_mgm — The NDB Cluster Management Client"> ndb_mgm </a> client <a class="link" href="mysql-cluster-backup-using-management-client.html" title="25.6.8.2 Using The NDB Cluster Management Client to Create a Backup"> <code class="literal"> START BACKUP </code> </a> command prior to performing the restart. Following the upgrade, restore the node or nodes using <a class="link" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup"> ndb_restore </a> . See <a class="xref" href="mysql-cluster-backup.html" title="25.6.8 Online Backup of NDB Cluster"> Section 25.6.8, “Online Backup of NDB Cluster” </a> , and <a class="xref" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup"> Section 25.5.23, “ndb_restore — Restore an NDB Cluster Backup” </a> , for more information. </li> <li class="listitem"> Use <a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program"> mysqldump </a> to create a backup prior to the upgrade; afterward, restore the dump using <a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement"> <code class="literal"> LOAD DATA </code> </a> . </li> </ul> </div> Resource Recovery. <a class="indexterm" name="idm46045092570592"> </a> To free memory previously allocated to a table by successive <a class="link" href="insert.html" title="15.2.7 INSERT Statement"> <code class="literal"> INSERT </code> </a> and <a class="link" href="delete.html" title="15.2.2 DELETE Statement"> <code class="literal"> DELETE </code> </a> operations, for re-use by other NDB Cluster tables. The process for performing a rolling restart may be generalized as follows: <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> Stop all cluster management nodes ( <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> processes), reconfigure them, then restart them. (See <a class="xref" href="mysql-cluster-rolling-restart.html#mysql-cluster-rolling-restart-multiple-ndb-mgmd" title="Rolling restarts with multiple management servers"> Rolling restarts with multiple management servers </a> .) </li> <li class="listitem"> Stop, reconfigure, then restart each cluster data node ( <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> ndbd </a> process) in turn. Some node configuration parameters can be updated by issuing <a class="link" href="mysql-cluster-mgm-client-commands.html#ndbclient-restart"> <code class="literal"> RESTART </code> </a> for each of the data nodes in the <a class="link" href="mysql-cluster-programs-ndb-mgm.html" title="25.5.5 ndb_mgm — The NDB Cluster Management Client"> ndb_mgm </a> client following the previous step. Other parameters require that the data node be stopped completely using the management client <a class="link" href="mysql-cluster-mgm-client-commands.html#ndbclient-stop"> <code class="literal"> STOP </code> </a> command, then started again from a system shell by invoking the <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> ndbd </a> or <a class="link" href="mysql-cluster-programs-ndbmtd.html" title="25.5.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)"> ndbmtd </a> executable as appropriate. (A shell command such as <a class="link" href="kill.html" title="15.7.8.4 KILL Statement"> kill </a> can also be used on most Unix systems to stop a data node process, but the <code class="literal"> STOP </code> command is preferred and usually simpler.) <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> On Windows, you can also use SC STOP and SC START commands, <code class="literal"> NET STOP </code> and <code class="literal"> NET START </code> commands, or the Windows Service Manager to stop and start nodes which have been installed as Windows services (see <a class="xref" href="mysql-cluster-install-windows-service.html" title="25.3.2.4 Installing NDB Cluster Processes as Windows Services"> Section 25.3.2.4, “Installing NDB Cluster Processes as Windows Services” </a> ). </div> The type of restart required is indicated in the documentation for each node configuration parameter. See <a class="xref" href="mysql-cluster-config-file.html" title="25.4.3 NDB Cluster Configuration Files"> Section 25.4.3, “NDB Cluster Configuration Files” </a> . </li> <li class="listitem"> Stop, reconfigure, then restart each cluster SQL node ( <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server"> mysqld </a> process) in turn. </li> </ol> </div> <a class="indexterm" name="idm46045092542352"> </a> NDB Cluster supports a somewhat flexible order for upgrading nodes. When upgrading an NDB Cluster, you may upgrade API nodes (including SQL nodes) before upgrading the management nodes, data nodes, or both. In other words, you are permitted to upgrade the API and SQL nodes in any order. This is subject to the following provisions: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> This functionality is intended for use as part of an online upgrade only. A mix of node binaries from different NDB Cluster releases is neither intended nor supported for continuous, long-term use in a production setting. </li> <li class="listitem"> You must upgrade all nodes of the same type (management, data, or API node) before upgrading any nodes of a different type. This remains true regardless of the order in which the nodes are upgraded. </li> <li class="listitem"> You must upgrade all management nodes before upgrading any data nodes. This remains true regardless of the order in which you upgrade the cluster's API and SQL nodes. </li> <li class="listitem"> Features specific to the “ new ” version must not be used until all management nodes and data nodes have been upgraded. This also applies to any MySQL Server version change that may apply, in addition to the NDB engine version change, so do not forget to take this into account when planning the upgrade. (This is true for online upgrades of NDB Cluster in general.) </li> </ul> </div> It is not possible for any API node to perform schema operations (such as data definition statements) during a node restart. Due in part to this limitation, schema operations are also not supported during an online upgrade or downgrade. In addition, it is not possible to perform native backups while an upgrade or downgrade is ongoing. <a name="mysql-cluster-rolling-restart-multiple-ndb-mgmd"> </a> Rolling restarts with multiple management servers. <a class="indexterm" name="idm46045092532384"> </a> <a class="indexterm" name="idm46045092530864"> </a> When performing a rolling restart of an NDB Cluster with multiple management nodes, you should keep in mind that <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> checks to see if any other management node is running, and, if so, tries to use that node's configuration data. To keep this from occurring, and to force <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> to re-read its configuration file, perform the following steps: <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> Stop all NDB Cluster <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> processes. </li> <li class="listitem"> Update all <code class="filename"> config.ini </code> files. </li> <li class="listitem"> Start a single <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> with <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_reload"> <code class="option"> --reload </code> </a> , <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_initial"> <code class="option"> --initial </code> </a> , or both options as desired. </li> <li class="listitem"> If you started the first <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> with the <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_initial"> <code class="option"> --initial </code> </a> option, you must also start any remaining <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> processes using <code class="option"> --initial </code> . Regardless of any other options used when starting the first <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> , you should not start any remaining <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> processes after the first one using <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_reload"> <code class="option"> --reload </code> </a> . </li> <li class="listitem"> Complete the rolling restarts of the data nodes and API nodes as normal. </li> </ol> </div> When performing a rolling restart to update the cluster's configuration, you can use the <code class="literal"> config_generation </code> column of the <a class="link" href="mysql-cluster-ndbinfo-nodes.html" title="25.6.17.48 The ndbinfo nodes Table"> <code class="literal"> ndbinfo.nodes </code> </a> table to keep track of which data nodes have been successfully restarted with the new configuration. See <a class="xref" href="mysql-cluster-ndbinfo-nodes.html" title="25.6.17.48 The ndbinfo nodes Table"> Section 25.6.17.48, “The ndbinfo nodes Table” </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/sys-latest-file-io.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="sys-latest-file-io"> </a> 30.4.3.15 The latest_file_io and x$latest_file_io Views </h4> </div> </div> </div> <a class="indexterm" name="idm46045062894000"> </a> <a class="indexterm" name="idm46045062892544"> </a> <a class="indexterm" name="idm46045062891056"> </a> <a class="indexterm" name="idm46045062889568"> </a> These views summarize file I/O activity, grouped by file and thread. By default, rows are sorted with most recent I/O first. The <a class="link" href="sys-latest-file-io.html" title="30.4.3.15 The latest_file_io and x$latest_file_io Views"> <code class="literal"> latest_file_io </code> </a> and <a class="link" href="sys-latest-file-io.html" title="30.4.3.15 The latest_file_io and x$latest_file_io Views"> <code class="literal"> x$latest_file_io </code> </a> views have these columns: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> thread </code> For foreground threads, the account associated with the thread (and port number for TCP/IP connections). For background threads, the thread name and thread ID </li> <li class="listitem"> <code class="literal"> file </code> The file path name. </li> <li class="listitem"> <code class="literal"> latency </code> The wait time of the file I/O event. </li> <li class="listitem"> <code class="literal"> operation </code> The type of operation. </li> <li class="listitem"> <code class="literal"> requested </code> The number of data bytes requested for the file I/O event. </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/create-logfile-group.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="create-logfile-group"> </a> 15.1.16 CREATE LOGFILE GROUP Statement </h3> </div> </div> </div> <a class="indexterm" name="idm46045187348880"> </a> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63712911"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">CREATE LOGFILE GROUP logfile_group ADD UNDOFILE 'undo_file' [INITIAL_SIZE [=] initial_size] [UNDO_BUFFER_SIZE [=] undo_buffer_size] [REDO_BUFFER_SIZE [=] redo_buffer_size] [NODEGROUP [=] nodegroup_id] [WAIT] [COMMENT [=] 'string'] ENGINE [=] engine_name</code></pre> </div> This statement creates a new log file group named <code> logfile_group </code> having a single undo file named ' <code> undo_file </code> '. A <a class="link" href="create-logfile-group.html" title="15.1.16 CREATE LOGFILE GROUP Statement"> <code class="literal"> CREATE LOGFILE GROUP </code> </a> statement has one and only one <code class="literal"> ADD UNDOFILE </code> clause. For rules covering the naming of log file groups, see <a class="xref" href="identifiers.html" title="11.2 Schema Object Names"> Section 11.2, “Schema Object Names” </a> . <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> All NDB Cluster Disk Data objects share the same namespace. This means that each Disk Data object must be uniquely named (and not merely each Disk Data object of a given type). For example, you cannot have a tablespace and a log file group with the same name, or a tablespace and a data file with the same name. </div> There can be only one log file group per NDB Cluster instance at any given time. The optional <code class="literal"> INITIAL_SIZE </code> parameter sets the undo file's initial size; if not specified, it defaults to <code class="literal"> 128M </code> (128 megabytes). The optional <code class="literal"> UNDO_BUFFER_SIZE </code> parameter sets the size used by the undo buffer for the log file group; The default value for <code class="literal"> UNDO_BUFFER_SIZE </code> is <code class="literal"> 8M </code> (eight megabytes); this value cannot exceed the amount of system memory available. Both of these parameters are specified in bytes. You may optionally follow either or both of these with a one-letter abbreviation for an order of magnitude, similar to those used in <code class="filename"> my.cnf </code> . Generally, this is one of the letters <code class="literal"> M </code> (for megabytes) or <code class="literal"> G </code> (for gigabytes). Memory used for <code class="literal"> UNDO_BUFFER_SIZE </code> comes from the global pool whose size is determined by the value of the <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-sharedglobalmemory"> <code class="literal"> SharedGlobalMemory </code> </a> data node configuration parameter. This includes any default value implied for this option by the setting of the <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-initiallogfilegroup"> <code class="literal"> InitialLogFileGroup </code> </a> data node configuration parameter. The maximum permitted for <code class="literal"> UNDO_BUFFER_SIZE </code> is 629145600 (600 MB). On 32-bit systems, the maximum supported value for <code class="literal"> INITIAL_SIZE </code> is 4294967296 (4 GB). (Bug #29186) The minimum allowed value for <code class="literal"> INITIAL_SIZE </code> is 1048576 (1 MB). The <code class="literal"> ENGINE </code> option determines the storage engine to be used by this log file group, with <code> engine_name </code> being the name of the storage engine. This must be <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> (or <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDBCLUSTER </code> </a> ). If <code class="literal"> ENGINE </code> is not set, MySQL tries to use the engine specified by the <a class="link" href="server-system-variables.html#sysvar_default_storage_engine"> <code class="literal"> default_storage_engine </code> </a> server system variable. In any case, if the engine is not specified as <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> or <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDBCLUSTER </code> </a> , the <code class="literal"> CREATE LOGFILE GROUP </code> statement appears to succeed but actually fails to create the log file group, as shown here: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa364070"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> CREATE LOGFILE GROUP lg1 -> ADD UNDOFILE 'undo.dat' INITIAL_SIZE = 10M; Query OK, 0 rows affected, 1 warning (0.00 sec) mysql> SHOW WARNINGS; +-------+------+------------------------------------------------------------------------------------------------+ | Level | Code | Message | +-------+------+------------------------------------------------------------------------------------------------+ | Error | 1478 | Table storage engine 'InnoDB' does not support the create option 'TABLESPACE or LOGFILE GROUP' | +-------+------+------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec) mysql> DROP LOGFILE GROUP lg1 ENGINE = NDB; ERROR 1529 (HY000): Failed to drop LOGFILE GROUP mysql> CREATE LOGFILE GROUP lg1 -> ADD UNDOFILE 'undo.dat' INITIAL_SIZE = 10M -> ENGINE = NDB; Query OK, 0 rows affected (2.97 sec)</code></pre> </div> The fact that the <code class="literal"> CREATE LOGFILE GROUP </code> statement does not actually return an error when a storage engine other than <code class="literal"> NDB </code> is specified, but rather appears to succeed, is a known issue which we hope to address in a future version of NDB Cluster. <code> REDO_BUFFER_SIZE </code> , <code class="literal"> NODEGROUP </code> , <code class="literal"> WAIT </code> , and <code class="literal"> COMMENT </code> are parsed but ignored, and so have no effect in MySQL 8.4. These options are intended for future expansion. When used with <code class="literal"> ENGINE [=] NDB </code> , a log file group and associated undo log file are created on each Cluster data node. You can verify that the undo files were created and obtain information about them by querying the Information Schema <a class="link" href="information-schema-files-table.html" title="28.3.15 The INFORMATION_SCHEMA FILES Table"> <code class="literal"> FILES </code> </a> table. For example: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47575318"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT LOGFILE_GROUP_NAME, LOGFILE_GROUP_NUMBER, EXTRA -> FROM INFORMATION_SCHEMA.FILES -> WHERE FILE_NAME = 'undo_10.dat'; +--------------------+----------------------+----------------+ | LOGFILE_GROUP_NAME | LOGFILE_GROUP_NUMBER | EXTRA | +--------------------+----------------------+----------------+ | lg_3 | 11 | CLUSTER_NODE=3 | | lg_3 | 11 | CLUSTER_NODE=4 | +--------------------+----------------------+----------------+ 2 rows in set (0.06 sec)</code></pre> </div> <a class="link" href="create-logfile-group.html" title="15.1.16 CREATE LOGFILE GROUP Statement"> <code class="literal"> CREATE LOGFILE GROUP </code> </a> is useful only with Disk Data storage for NDB Cluster. See <a class="xref" href="mysql-cluster-disk-data.html" title="25.6.11 NDB Cluster Disk Data Tables"> Section 25.6.11, “NDB Cluster Disk Data Tables” </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/optimize-blob.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="optimize-blob"> </a> 10.4.2.3 Optimizing for BLOB Types </h4> </div> </div> </div> <a class="indexterm" name="idm46045226748016"> </a> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> When storing a large blob containing textual data, consider compressing it first. Do not use this technique when the entire table is compressed by <code class="literal"> InnoDB </code> or <code class="literal"> MyISAM </code> . </li> <li class="listitem"> For a table with several columns, to reduce memory requirements for queries that do not use the BLOB column, consider splitting the BLOB column into a separate table and referencing it with a join query when needed. </li> <li class="listitem"> Since the performance requirements to retrieve and display a BLOB value might be very different from other data types, you could put the BLOB-specific table on a different storage device or even a separate database instance. For example, to retrieve a BLOB might require a large sequential disk read that is better suited to a traditional hard drive than to an <a class="link" href="glossary.html#glos_ssd" title="SSD"> SSD device </a> . </li> <li class="listitem"> See <a class="xref" href="optimize-character.html" title="10.4.2.2 Optimizing for Character and String Types"> Section 10.4.2.2, “Optimizing for Character and String Types” </a> for reasons why a binary <code class="literal"> VARCHAR </code> column is sometimes preferable to an equivalent BLOB column. </li> <li class="listitem"> Rather than testing for equality against a very long text string, you can store a hash of the column value in a separate column, index that column, and test the hashed value in queries. (Use the <code class="literal"> MD5() </code> or <code class="literal"> CRC32() </code> function to produce the hash value.) Since hash functions can produce duplicate results for different inputs, you still include a clause <code class="literal"> AND <code> blob_column </code> = <code> long_string_value </code> </code> in the query to guard against false matches; the performance benefit comes from the smaller, easily scanned index for the hashed values. </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/describe.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="describe"> </a> 15.8.1 DESCRIBE Statement </h3> </div> </div> </div> <a class="indexterm" name="idm46045168208224"> </a> <a class="indexterm" name="idm46045168207152"> </a> The <a class="link" href="describe.html" title="15.8.1 DESCRIBE Statement"> <code class="literal"> DESCRIBE </code> </a> and <a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement"> <code class="literal"> EXPLAIN </code> </a> statements are synonyms, used either to obtain information about table structure or query execution plans. For more information, see <a class="xref" href="show-columns.html" title="15.7.7.6 SHOW COLUMNS Statement"> Section 15.7.7.6, “SHOW COLUMNS Statement” </a> , and <a class="xref" href="explain.html" title="15.8.2 EXPLAIN Statement"> Section 15.8.2, “EXPLAIN Statement” </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/group-replication-operations.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="group-replication-operations"> </a> 20.5 Group Replication Operations </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <a href="group-replication-configuring-online-group.html"> 20.5.1 Configuring an Online Group </a> </dt> <dt> <a href="group-replication-restarting-group.html"> 20.5.2 Restarting a Group </a> </dt> <dt> <a href="group-replication-consistency-guarantees.html"> 20.5.3 Transaction Consistency Guarantees </a> </dt> <dt> <a href="group-replication-distributed-recovery.html"> 20.5.4 Distributed Recovery </a> </dt> <dt> <a href="group-replication-ipv6.html"> 20.5.5 Support For IPv6 And For Mixed IPv6 And IPv4 Groups </a> </dt> <dt> <a href="group-replication-enterprise-backup.html"> 20.5.6 Using MySQL Enterprise Backup with Group Replication </a> </dt> </dl> </div> <a class="indexterm" name="idm46045133625440"> </a> This section explains common operations for managing groups. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/telemetry-trace.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="telemetry-trace"> </a> 35.3 OpenTelemetry Trace </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <a href="telemetry-trace-configuration.html"> 35.3.1 Configuring Trace Telemetry </a> </dt> <dt> <a href="telemetry-trace-format.html"> 35.3.2 Trace Format </a> </dt> </dl> </div> Tracing telemetry enables you to visualize the flow of any processing action as it is processed through your server. The data for each action, a span, includes possible error information and timing data. Traces are generated for <code class="literal"> COM_QUERY </code> commands executed, including non-query commands such as <code class="literal"> COM_PING </code> , or <code class="literal"> COM_STMT_CLOSE </code> . Query statement traces also have an associated SQL text attribute. Telemetry tracing is implemented in: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> MySQL Enterprise Edition Telemetry Component </li> <li class="listitem"> MySQL Enterprise Edition Client </li> <li class="listitem"> MySQL Connectors </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/optimizing-memory-tables.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="optimizing-memory-tables"> </a> 10.7 Optimizing for MEMORY Tables </h2> </div> </div> </div> <a class="indexterm" name="idm46045225633552"> </a> Consider using <code class="literal"> MEMORY </code> tables for noncritical data that is accessed often, and is read-only or rarely updated. Benchmark your application against equivalent <code class="literal"> InnoDB </code> or <code class="literal"> MyISAM </code> tables under a realistic workload, to confirm that any additional performance is worth the risk of losing data, or the overhead of copying data from a disk-based table at application start. For best performance with <code class="literal"> MEMORY </code> tables, examine the kinds of queries against each table, and specify the type to use for each associated index, either a B-tree index or a hash index. On the <a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement"> <code class="literal"> CREATE INDEX </code> </a> statement, use the clause <code class="literal"> USING BTREE </code> or <code class="literal"> USING HASH </code> . B-tree indexes are fast for queries that do greater-than or less-than comparisons through operators such as <code class="literal"> > </code> or <code class="literal"> BETWEEN </code> . Hash indexes are only fast for queries that look up single values through the <code class="literal"> = </code> operator, or a restricted set of values through the <code class="literal"> IN </code> operator. For why <code class="literal"> USING BTREE </code> is often a better choice than the default <code class="literal"> USING HASH </code> , see <a class="xref" href="table-scan-avoidance.html" title="10.2.1.23 Avoiding Full Table Scans"> Section 10.2.1.23, “Avoiding Full Table Scans” </a> . For implementation details of the different types of <code class="literal"> MEMORY </code> indexes, see <a class="xref" href="index-btree-hash.html" title="10.3.9 Comparison of B-Tree and Hash Indexes"> Section 10.3.9, “Comparison of B-Tree and Hash Indexes” </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/replication-threads-monitor-main.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="replication-threads-monitor-main"> </a> 19.2.3.1 Monitoring Replication Main Threads </h4> </div> </div> </div> The <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> statement provides information that tells you what is happening on the source and on the replica regarding replication. For information on source states, see <a class="xref" href="source-thread-states.html" title="10.14.4 Replication Source Thread States"> Section 10.14.4, “Replication Source Thread States” </a> . For replica states, see <a class="xref" href="replica-io-thread-states.html" title="10.14.5 Replication I/O (Receiver) Thread States"> Section 10.14.5, “Replication I/O (Receiver) Thread States” </a> , and <a class="xref" href="replica-sql-thread-states.html" title="10.14.6 Replication SQL Thread States"> Section 10.14.6, “Replication SQL Thread States” </a> . The following example illustrates how the three main replication threads, the binary log dump thread, replication I/O (receiver) thread, and replication SQL (applier) thread, show up in the output from <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> . On the source server, the output from <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> looks like this: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa53453033"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SHOW PROCESSLIST\G *************************** 1. row *************************** Id: 2 User: root Host: localhost:32931 db: NULL Command: Binlog Dump Time: 94 State: Has sent all binlog to slave; waiting for binlog to be updated Info: NULL</code></pre> </div> Here, thread 2 is a <code class="literal"> Binlog Dump </code> thread that services a connected replica. The <code class="literal"> State </code> information indicates that all outstanding updates have been sent to the replica and that the source is waiting for more updates to occur. If you see no <code class="literal"> Binlog Dump </code> threads on a source server, this means that replication is not running; that is, no replicas are currently connected. On a replica server, the output from <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> looks like this: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa82414362"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SHOW PROCESSLIST\G *************************** 1. row *************************** Id: 10 User: system user Host: db: NULL Command: Connect Time: 11 State: Waiting for master to send event Info: NULL *************************** 2. row *************************** Id: 11 User: system user Host: db: NULL Command: Connect Time: 11 State: Has read all relay log; waiting for the slave I/O thread to update it Info: NULL</code></pre> </div> The <code class="literal"> State </code> information indicates that thread 10 is the replication I/O (receiver) thread that is communicating with the source server, and thread 11 is the replication SQL (applier) thread that is processing the updates stored in the relay logs. At the time that <a class="link" href="show-processlist.html" title="15.7.7.31 SHOW PROCESSLIST Statement"> <code class="literal"> SHOW PROCESSLIST </code> </a> was run, both threads were idle, waiting for further updates. The value in the <code class="literal"> Time </code> column can show how late the replica is compared to the source. See <a class="xref" href="faqs-replication.html" title="A.14 MySQL 8.4 FAQ: Replication"> Section A.14, “MySQL 8.4 FAQ: Replication” </a> . If sufficient time elapses on the source side without activity on the <code class="literal"> Binlog Dump </code> thread, the source determines that the replica is no longer connected. As for any other client connection, the timeouts for this depend on the values of <code class="option"> net_write_timeout </code> and <code class="option"> net_retry_count </code> ; for more information about these, see <a class="xref" href="server-system-variables.html" title="7.1.8 Server System Variables"> Section 7.1.8, “Server System Variables” </a> . The <a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement"> <code class="literal"> SHOW REPLICA STATUS </code> </a> statement provides additional information about replication processing on a replica server. See <a class="xref" href="replication-administration-status.html" title="19.1.7.1 Checking Replication Status"> Section 19.1.7.1, “Checking Replication Status” </a> . You can also retrieve information on the source's <code class="literal"> Binlog Dump </code> threads with the following: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa2700930"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql"> SELECT * FROM performance_schema.threads WHERE PROCESSLIST_COMMAND LIKE "Binlog Dump%"</code></pre> </div> <code class="literal"> Binlog Dump% </code> is used to retrieve either <code class="literal"> Binlog Dump </code> or <code class="literal"> Binlog Dump GTID </code> , depending on which mode binlog dumping is in. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/partitioning-management-hash-key.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="partitioning-management-hash-key"> </a> 26.3.2 Management of HASH and KEY Partitions </h3> </div> </div> </div> <a class="indexterm" name="idm46045083734704"> </a> <a class="indexterm" name="idm46045083733216"> </a> <a class="indexterm" name="idm46045083731728"> </a> <a class="indexterm" name="idm46045083730240"> </a> Tables which are partitioned by hash or by key are very similar to one another with regard to making changes in a partitioning setup, and both differ in a number of ways from tables which have been partitioned by range or list. For that reason, this section addresses the modification of tables partitioned by hash or by key only. For a discussion of adding and dropping of partitions of tables that are partitioned by range or list, see <a class="xref" href="partitioning-management-range-list.html" title="26.3.1 Management of RANGE and LIST Partitions"> Section 26.3.1, “Management of RANGE and LIST Partitions” </a> . You cannot drop partitions from tables that are partitioned by <code class="literal"> HASH </code> or <code class="literal"> KEY </code> in the same way that you can from tables that are partitioned by <code class="literal"> RANGE </code> or <code class="literal"> LIST </code> . However, you can merge <code class="literal"> HASH </code> or <code class="literal"> KEY </code> partitions using <code class="literal"> ALTER TABLE ... COALESCE PARTITION </code> . Suppose that a <code class="literal"> clients </code> table containing data about clients is divided into 12 partitions, created as shown here: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa79414721"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">CREATE TABLE clients ( id INT, fname VARCHAR(30), lname VARCHAR(30), signed DATE ) PARTITION BY HASH( MONTH(signed) ) PARTITIONS 12;</code></pre> </div> To reduce the number of partitions from 12 to 8, execute the following <a class="link" href="alter-table-partition-operations.html" title="15.1.9.1 ALTER TABLE Partition Operations"> <code class="literal"> ALTER TABLE </code> </a> statement: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47927222"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> ALTER TABLE clients COALESCE PARTITION 4; Query OK, 0 rows affected (0.02 sec)</code></pre> </div> <code class="literal"> COALESCE </code> works equally well with tables that are partitioned by <code class="literal"> HASH </code> , <code class="literal"> KEY </code> , <code class="literal"> LINEAR HASH </code> , or <code class="literal"> LINEAR KEY </code> . Here is an example similar to the previous one, differing only in that the table is partitioned by <code class="literal"> LINEAR KEY </code> : <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81483131"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> CREATE TABLE clients_lk ( -> id INT, -> fname VARCHAR(30), -> lname VARCHAR(30), -> signed DATE -> ) -> PARTITION BY LINEAR KEY(signed) -> PARTITIONS 12; Query OK, 0 rows affected (0.03 sec) mysql> ALTER TABLE clients_lk COALESCE PARTITION 4; Query OK, 0 rows affected (0.06 sec) Records: 0 Duplicates: 0 Warnings: 0</code></pre> </div> The number following <code class="literal"> COALESCE PARTITION </code> is the number of partitions to merge into the remainder—in other words, it is the number of partitions to remove from the table. Attempting to remove more partitions than are in the table results in an error like this one: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa14288683"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> ALTER TABLE clients COALESCE PARTITION 18; ERROR 1478 (HY000): Cannot remove all partitions, use DROP TABLE instead</code></pre> </div> To increase the number of partitions for the <code class="literal"> clients </code> table from 12 to 18, use <code class="literal"> ALTER TABLE ... ADD PARTITION </code> as shown here: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa48382134"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">ALTER TABLE clients ADD PARTITION PARTITIONS 6;</code></pre> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/group-replication-functions-for-communication-protocol.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="group-replication-functions-for-communication-protocol"> </a> 14.18.1.4 Functions to Inspect and Set the Group Replication Communication Protocol Version </h4> </div> </div> </div> The following functions enable you to inspect and configure the Group Replication communication protocol version that is used by a replication group. <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <a class="xref" href="group-replication-message-compression.html" title="20.7.4 Message Compression"> Section 20.7.4, “Message Compression” </a> </li> <li class="listitem"> <a class="xref" href="group-replication-performance-message-fragmentation.html" title="20.7.5 Message Fragmentation"> Section 20.7.5, “Message Fragmentation” </a> </li> <li class="listitem"> <a class="xref" href="group-replication-single-consensus-leader.html" title="20.7.3 Single Consensus Leader"> Section 20.7.3, “Single Consensus Leader” </a> </li> </ul> </div> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <a name="function_group-replication-get-communication-protocol"> </a> <a class="link" href="group-replication-functions-for-communication-protocol.html#function_group-replication-get-communication-protocol"> <code class="literal"> group_replication_get_communication_protocol() </code> </a> <a class="indexterm" name="idm46045193806336"> </a> <a class="indexterm" name="idm46045193805232"> </a> Inspect the Group Replication communication protocol version that is currently in use for a group. Syntax: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-clike"><div class="docs-select-all right" id="sa80884479"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-clike">STRING group_replication_get_communication_protocol()</code></pre> </div> This function has no parameters. Return value: The oldest MySQL Server version that can join this group and use the group's communication protocol. Note that the <a class="link" href="group-replication-functions-for-communication-protocol.html#function_group-replication-get-communication-protocol"> <code class="literal"> group_replication_get_communication_protocol() </code> </a> function returns the minimum MySQL version that the group supports, which might differ from the version number that was passed to <a class="link" href="group-replication-functions-for-communication-protocol.html#function_group-replication-set-communication-protocol"> <code class="literal"> group_replication_set_communication_protocol() </code> </a> , and from the MySQL Server version that is installed on the member where you use the function. If the protocol cannot be inspected because this server instance does not belong to a replication group, an error is returned as a string. Example: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa13525648"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SELECT group_replication_get_communication_protocol(); +------------------------------------------------+ | group_replication_get_communication_protocol() | +------------------------------------------------+ | 8.4.3 | +------------------------------------------------+</code></pre> </div> For more information, see <a class="xref" href="group-replication-communication-protocol.html" title="20.5.1.4 Setting a Group's Communication Protocol Version"> Section 20.5.1.4, “Setting a Group's Communication Protocol Version” </a> . </li> <li class="listitem"> <a name="function_group-replication-set-communication-protocol"> </a> <a class="link" href="group-replication-functions-for-communication-protocol.html#function_group-replication-set-communication-protocol"> <code class="literal"> group_replication_set_communication_protocol() </code> </a> <a class="indexterm" name="idm46045193790576"> </a> <a class="indexterm" name="idm46045193789472"> </a> Downgrade the Group Replication communication protocol version of a group so that members at earlier releases can join, or upgrade the Group Replication communication protocol version of a group after upgrading MySQL Server on all members. The <a class="link" href="privileges-provided.html#priv_group-replication-admin"> <code class="literal"> GROUP_REPLICATION_ADMIN </code> </a> privilege is required to use this function, and all existing group members must be online when you issue the statement, with no loss of majority. <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> For MySQL InnoDB cluster, the communication protocol version is managed automatically whenever the cluster topology is changed using AdminAPI operations. You do not have to use these functions yourself for an InnoDB cluster. </div> Syntax: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-clike"><div class="docs-select-all right" id="sa88979436"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-clike">STRING group_replication_set_communication_protocol(version)</code></pre> </div> Arguments: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <code> version </code> : For a downgrade, specify the MySQL Server version of the prospective group member that has the oldest installed server version. In this case, the command makes the group fall back to a communication protocol compatible with that server version if possible. The minimum server version that you can specify is MySQL 5.7.14. For an upgrade, specify the new MySQL Server version to which the existing group members have been upgraded. </li> </ul> </div> Return value: A string containing the result of the operation, for example whether it was successful or not. Example: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa38721772"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SELECT group_replication_set_communication_protocol("5.7.25");</code></pre> </div> For more information, see <a class="xref" href="group-replication-communication-protocol.html" title="20.5.1.4 Setting a Group's Communication Protocol Version"> Section 20.5.1.4, “Setting a Group's Communication Protocol Version” </a> . </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/window-functions-named-windows.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="window-functions-named-windows"> </a> 14.20.4 Named Windows </h3> </div> </div> </div> <a class="indexterm" name="idm46045191776896"> </a> <a class="indexterm" name="idm46045191775408"> </a> Windows can be defined and given names by which to refer to them in <code class="literal"> OVER </code> clauses. To do this, use a <code class="literal"> WINDOW </code> clause. If present in a query, the <code class="literal"> WINDOW </code> clause falls between the positions of the <code class="literal"> HAVING </code> and <code class="literal"> ORDER BY </code> clauses, and has this syntax: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa32405680"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">WINDOW window_name AS (window_spec) [, window_name AS (window_spec)] ...</code></pre> </div> For each window definition, <code> window_name </code> is the window name, and <code> window_spec </code> is the same type of window specification as given between the parentheses of an <code class="literal"> OVER </code> clause, as described in <a class="xref" href="window-functions-usage.html" title="14.20.2 Window Function Concepts and Syntax"> Section 14.20.2, “Window Function Concepts and Syntax” </a> : <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa18744139"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">window_spec: [window_name] [partition_clause] [order_clause] [frame_clause]</code></pre> </div> A <code class="literal"> WINDOW </code> clause is useful for queries in which multiple <code class="literal"> OVER </code> clauses would otherwise define the same window. Instead, you can define the window once, give it a name, and refer to the name in the <code class="literal"> OVER </code> clauses. Consider this query, which defines the same window multiple times: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75536678"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SELECT val, ROW_NUMBER() OVER (ORDER BY val) AS 'row_number', RANK() OVER (ORDER BY val) AS 'rank', DENSE_RANK() OVER (ORDER BY val) AS 'dense_rank' FROM numbers;</code></pre> </div> The query can be written more simply by using <code class="literal"> WINDOW </code> to define the window once and referring to the window by name in the <code class="literal"> OVER </code> clauses: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa66633455"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SELECT val, ROW_NUMBER() OVER w AS 'row_number', RANK() OVER w AS 'rank', DENSE_RANK() OVER w AS 'dense_rank' FROM numbers WINDOW w AS (ORDER BY val);</code></pre> </div> A named window also makes it easier to experiment with the window definition to see the effect on query results. You need only modify the window definition in the <code class="literal"> WINDOW </code> clause, rather than multiple <code class="literal"> OVER </code> clause definitions. If an <code class="literal"> OVER </code> clause uses <code class="literal"> OVER ( <code> window_name </code> ...) </code> rather than <code class="literal"> OVER <code> window_name </code> </code> , the named window can be modified by the addition of other clauses. For example, this query defines a window that includes partitioning, and uses <code class="literal"> ORDER BY </code> in the <code class="literal"> OVER </code> clauses to modify the window in different ways: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa21721618"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SELECT DISTINCT year, country, FIRST_VALUE(year) OVER (w ORDER BY year ASC) AS first, FIRST_VALUE(year) OVER (w ORDER BY year DESC) AS last FROM sales WINDOW w AS (PARTITION BY country);</code></pre> </div> An <code class="literal"> OVER </code> clause can only add properties to a named window, not modify them. If the named window definition includes a partitioning, ordering, or framing property, the <code class="literal"> OVER </code> clause that refers to the window name cannot also include the same kind of property or an error occurs: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> This construct is permitted because the window definition and the referring <code class="literal"> OVER </code> clause do not contain the same kind of properties: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa42050195"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">OVER (w ORDER BY country) ... WINDOW w AS (PARTITION BY country)</code></pre> </div> </li> <li class="listitem"> This construct is not permitted because the <code class="literal"> OVER </code> clause specifies <code class="literal"> PARTITION BY </code> for a named window that already has <code class="literal"> PARTITION BY </code> : <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa7991103"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">OVER (w PARTITION BY year) ... WINDOW w AS (PARTITION BY country)</code></pre> </div> </li> </ul> </div> The definition of a named window can itself begin with a <code> window_name </code> . In such cases, forward and backward references are permitted, but not cycles: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> This is permitted; it contains forward and backward references but no cycles: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa61675262"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">WINDOW w1 AS (w2), w2 AS (), w3 AS (w1)</code></pre> </div> </li> <li class="listitem"> This is not permitted because it contains a cycle: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa94529933"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">WINDOW w1 AS (w2), w2 AS (w3), w3 AS (w1)</code></pre> </div> </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/permission-optimization.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="permission-optimization"> </a> 10.2.6 Optimizing Database Privileges </h3> </div> </div> </div> <a class="indexterm" name="idm46045227611008"> </a> <a class="indexterm" name="idm46045227609552"> </a> The more complex your privilege setup, the more overhead applies to all SQL statements. Simplifying the privileges established by <a class="link" href="grant.html" title="15.7.1.6 GRANT Statement"> <code class="literal"> GRANT </code> </a> statements enables MySQL to reduce permission-checking overhead when clients execute statements. For example, if you do not grant any table-level or column-level privileges, the server need not ever check the contents of the <code class="literal"> tables_priv </code> and <code class="literal"> columns_priv </code> tables. Similarly, if you place no resource limits on any accounts, the server does not have to perform resource counting. If you have a very high statement-processing load, consider using a simplified grant structure to reduce permission-checking overhead. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/show-procedure-status.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="show-procedure-status"> </a> 15.7.7.30 SHOW PROCEDURE STATUS Statement </h4> </div> </div> </div> <a class="indexterm" name="idm46045169953648"> </a> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34616638"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SHOW PROCEDURE STATUS [LIKE 'pattern' | WHERE expr]</code></pre> </div> This statement is a MySQL extension. It returns characteristics of a stored procedure, such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, <a class="link" href="show-function-status.html" title="15.7.7.21 SHOW FUNCTION STATUS Statement"> <code class="literal"> SHOW FUNCTION STATUS </code> </a> , displays information about stored functions (see <a class="xref" href="show-function-status.html" title="15.7.7.21 SHOW FUNCTION STATUS Statement"> Section 15.7.7.21, “SHOW FUNCTION STATUS Statement” </a> ). To use either statement, you must be the user named as the routine <code class="literal"> DEFINER </code> , have the <a class="link" href="privileges-provided.html#priv_show-routine"> <code class="literal"> SHOW_ROUTINE </code> </a> privilege, have the <a class="link" href="privileges-provided.html#priv_select"> <code class="literal"> SELECT </code> </a> privilege at the global level, or have the <a class="link" href="privileges-provided.html#priv_create-routine"> <code class="literal"> CREATE ROUTINE </code> </a> , <a class="link" href="privileges-provided.html#priv_alter-routine"> <code class="literal"> ALTER ROUTINE </code> </a> , or <a class="link" href="privileges-provided.html#priv_execute"> <code class="literal"> EXECUTE </code> </a> privilege granted at a scope that includes the routine. The <a class="link" href="string-comparison-functions.html#operator_like"> <code class="literal"> LIKE </code> </a> clause, if present, indicates which procedure or function names to match. The <code class="literal"> WHERE </code> clause can be given to select rows using more general conditions, as discussed in <a class="xref" href="extended-show.html" title="28.8 Extensions to SHOW Statements"> Section 28.8, “Extensions to SHOW Statements” </a> . <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16724578"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SHOW PROCEDURE STATUS LIKE 'sp1'\G *************************** 1. row *************************** Db: test Name: sp1 Type: PROCEDURE Definer: testuser@localhost Modified: 2018-08-08 13:54:11 Created: 2018-08-08 13:54:11 Security_type: DEFINER Comment: character_set_client: utf8mb4 collation_connection: utf8mb4_0900_ai_ci Database Collation: utf8mb4_0900_ai_ci mysql> SHOW FUNCTION STATUS LIKE 'hello'\G *************************** 1. row *************************** Db: test Name: hello Type: FUNCTION Definer: testuser@localhost Modified: 2020-03-10 11:10:03 Created: 2020-03-10 11:10:03 Security_type: DEFINER Comment: character_set_client: utf8mb4 collation_connection: utf8mb4_0900_ai_ci Database Collation: utf8mb4_0900_ai_ci</code></pre> </div> <code class="literal"> character_set_client </code> is the session value of the <a class="link" href="server-system-variables.html#sysvar_character_set_client"> <code class="literal"> character_set_client </code> </a> system variable when the routine was created. <code class="literal"> collation_connection </code> is the session value of the <a class="link" href="server-system-variables.html#sysvar_collation_connection"> <code class="literal"> collation_connection </code> </a> system variable when the routine was created. <code class="literal"> Database Collation </code> is the collation of the database with which the routine is associated. Stored routine information is also available from the <code class="literal"> INFORMATION_SCHEMA </code> <a class="link" href="information-schema-parameters-table.html" title="28.3.20 The INFORMATION_SCHEMA PARAMETERS Table"> <code class="literal"> PARAMETERS </code> </a> and <a class="link" href="information-schema-routines-table.html" title="28.3.30 The INFORMATION_SCHEMA ROUTINES Table"> <code class="literal"> ROUTINES </code> </a> tables. See <a class="xref" href="information-schema-parameters-table.html" title="28.3.20 The INFORMATION_SCHEMA PARAMETERS Table"> Section 28.3.20, “The INFORMATION_SCHEMA PARAMETERS Table” </a> , and <a class="xref" href="information-schema-routines-table.html" title="28.3.30 The INFORMATION_SCHEMA ROUTINES Table"> Section 28.3.30, “The INFORMATION_SCHEMA ROUTINES Table” </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/performance-schema-statement-summary-tables.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="performance-schema-statement-summary-tables"> </a> 29.12.20.3 Statement Summary Tables </h4> </div> </div> </div> <a class="indexterm" name="idm46045068967088"> </a> <a class="indexterm" name="idm46045068965552"> </a> <a class="indexterm" name="idm46045068964016"> </a> <a class="indexterm" name="idm46045068962560"> </a> <a class="indexterm" name="idm46045068961040"> </a> <a class="indexterm" name="idm46045068959520"> </a> <a class="indexterm" name="idm46045068958000"> </a> <a class="indexterm" name="idm46045068956480"> </a> <a class="indexterm" name="idm46045068954960"> </a> <a class="indexterm" name="idm46045068953440"> </a> <a class="indexterm" name="idm46045068951920"> </a> <a class="indexterm" name="idm46045068950400"> </a> <a class="indexterm" name="idm46045068948880"> </a> <a class="indexterm" name="idm46045068947360"> </a> <a class="indexterm" name="idm46045068945840"> </a> <a class="indexterm" name="idm46045068944336"> </a> The Performance Schema maintains tables for collecting current and recent statement events, and aggregates that information in summary tables. <a class="xref" href="performance-schema-statement-tables.html" title="29.12.6 Performance Schema Statement Event Tables"> Section 29.12.6, “Performance Schema Statement Event Tables” </a> describes the events on which statement summaries are based. See that discussion for information about the content of statement events, the current and historical statement event tables, and how to control statement event collection, which is partially disabled by default. Example statement event summary information: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa525453"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT * FROM performance_schema.events_statements_summary_global_by_event_name\G *************************** 1. row *************************** EVENT_NAME: statement/sql/select COUNT_STAR: 54 SUM_TIMER_WAIT: 38860400000 MIN_TIMER_WAIT: 52400000 AVG_TIMER_WAIT: 719600000 MAX_TIMER_WAIT: 12631800000 SUM_LOCK_TIME: 88000000 SUM_ERRORS: 0 SUM_WARNINGS: 0 SUM_ROWS_AFFECTED: 0 SUM_ROWS_SENT: 60 SUM_ROWS_EXAMINED: 120 SUM_CREATED_TMP_DISK_TABLES: 0 SUM_CREATED_TMP_TABLES: 21 SUM_SELECT_FULL_JOIN: 16 SUM_SELECT_FULL_RANGE_JOIN: 0 SUM_SELECT_RANGE: 0 SUM_SELECT_RANGE_CHECK: 0 SUM_SELECT_SCAN: 41 SUM_SORT_MERGE_PASSES: 0 SUM_SORT_RANGE: 0 SUM_SORT_ROWS: 0 SUM_SORT_SCAN: 0 SUM_NO_INDEX_USED: 22 SUM_NO_GOOD_INDEX_USED: 0 SUM_CPU_TIME: 0 MAX_CONTROLLED_MEMORY: 2028360 MAX_TOTAL_MEMORY: 2853429 COUNT_SECONDARY: 0 ...</code></pre> </div> Each statement summary table has one or more grouping columns to indicate how the table aggregates events. Event names refer to names of event instruments in the <a class="link" href="performance-schema-setup-instruments-table.html" title="29.12.2.3 The setup_instruments Table"> <code class="literal"> setup_instruments </code> </a> table: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_account_by_event_name </code> </a> has <code class="literal"> EVENT_NAME </code> , <code class="literal"> USER </code> , and <code class="literal"> HOST </code> columns. Each row summarizes events for a given account (user and host combination) and event name. </li> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> has <code class="literal"> SCHEMA_NAME </code> and <code class="literal"> DIGEST </code> columns. Each row summarizes events per schema and digest value. (The <code class="literal"> DIGEST_TEXT </code> column contains the corresponding normalized statement digest text, but is neither a grouping nor a summary column. The <code class="literal"> QUERY_SAMPLE_TEXT </code> , <code class="literal"> QUERY_SAMPLE_SEEN </code> , and <code class="literal"> QUERY_SAMPLE_TIMER_WAIT </code> columns also are neither grouping nor summary columns; they support statement sampling.) The maximum number of rows in the table is autosized at server startup. To set this maximum explicitly, set the <a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_digests_size"> <code class="literal"> performance_schema_digests_size </code> </a> system variable at server startup. </li> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_host_by_event_name </code> </a> has <code class="literal"> EVENT_NAME </code> and <code class="literal"> HOST </code> columns. Each row summarizes events for a given host and event name. </li> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_program </code> </a> has <code class="literal"> OBJECT_TYPE </code> , <code class="literal"> OBJECT_SCHEMA </code> , and <code class="literal"> OBJECT_NAME </code> columns. Each row summarizes events for a given stored program (stored procedure or function, trigger, or event). </li> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_thread_by_event_name </code> </a> has <code class="literal"> THREAD_ID </code> and <code class="literal"> EVENT_NAME </code> columns. Each row summarizes events for a given thread and event name. </li> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_user_by_event_name </code> </a> has <code class="literal"> EVENT_NAME </code> and <code class="literal"> USER </code> columns. Each row summarizes events for a given user and event name. </li> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_global_by_event_name </code> </a> has an <code class="literal"> EVENT_NAME </code> column. Each row summarizes events for a given event name. </li> <li class="listitem"> <a class="link" href="performance-schema-prepared-statements-instances-table.html" title="29.12.6.4 The prepared_statements_instances Table"> <code class="literal"> prepared_statements_instances </code> </a> has an <code class="literal"> OBJECT_INSTANCE_BEGIN </code> column. Each row summarizes events for a given prepared statement. </li> </ul> </div> Each statement summary table has these summary columns containing aggregated values (with exceptions as noted): <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> COUNT_STAR </code> , <code class="literal"> SUM_TIMER_WAIT </code> , <code class="literal"> MIN_TIMER_WAIT </code> , <code class="literal"> AVG_TIMER_WAIT </code> , <code class="literal"> MAX_TIMER_WAIT </code> These columns are analogous to the columns of the same names in the wait event summary tables (see <a class="xref" href="performance-schema-wait-summary-tables.html" title="29.12.20.1 Wait Event Summary Tables"> Section 29.12.20.1, “Wait Event Summary Tables” </a> ), except that the statement summary tables aggregate events from <a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table"> <code class="literal"> events_statements_current </code> </a> rather than <a class="link" href="performance-schema-events-waits-current-table.html" title="29.12.4.1 The events_waits_current Table"> <code class="literal"> events_waits_current </code> </a> . The <a class="link" href="performance-schema-prepared-statements-instances-table.html" title="29.12.6.4 The prepared_statements_instances Table"> <code class="literal"> prepared_statements_instances </code> </a> table does not have these columns. </li> <li class="listitem"> <code class="literal"> SUM_ <code> xxx </code> </code> The aggregate of the corresponding <code> xxx </code> column in the <a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table"> <code class="literal"> events_statements_current </code> </a> table. For example, the <code class="literal"> SUM_LOCK_TIME </code> and <code class="literal"> SUM_ERRORS </code> columns in statement summary tables are the aggregates of the <code class="literal"> LOCK_TIME </code> and <code class="literal"> ERRORS </code> columns in <a class="link" href="performance-schema-events-statements-current-table.html" title="29.12.6.1 The events_statements_current Table"> <code class="literal"> events_statements_current </code> </a> table. </li> <li class="listitem"> <code class="literal"> MAX_CONTROLLED_MEMORY </code> Reports the maximum amount of controlled memory used by a statement during execution. </li> <li class="listitem"> <code class="literal"> MAX_TOTAL_MEMORY </code> Reports the maximum amount of memory used by a statement during execution. </li> <li class="listitem"> <code class="literal"> COUNT_SECONDARY </code> The number of times a query was processed on the <code class="literal"> SECONDARY </code> engine. For use with HeatWave Service and HeatWave, where the <code class="literal"> PRIMARY </code> engine is <code class="literal"> InnoDB </code> and the <code class="literal"> SECONDARY </code> engine is HeatWave ( <code class="literal"> RAPID </code> ). For MySQL Community Edition Server, MySQL Enterprise Edition Server (on-premise), and HeatWave Service without HeatWave, queries are always processed on the <code class="literal"> PRIMARY </code> engine, which means the value is always 0 on these MySQL Servers. </li> </ul> </div> The <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> table has these additional summary columns: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> FIRST_SEEN </code> , <code class="literal"> LAST_SEEN </code> Timestamps indicating when statements with the given digest value were first seen and most recently seen. </li> <li class="listitem"> <code class="literal"> QUANTILE_95 </code> : The 95th percentile of the statement latency, in picoseconds. This percentile is a high estimate, computed from the histogram data collected. In other words, for a given digest, 95% of the statements measured have a latency lower than <code class="literal"> QUANTILE_95 </code> . For access to the histogram data, use the tables described in <a class="xref" href="performance-schema-statement-histogram-summary-tables.html" title="29.12.20.4 Statement Histogram Summary Tables"> Section 29.12.20.4, “Statement Histogram Summary Tables” </a> . </li> <li class="listitem"> <code class="literal"> QUANTILE_99 </code> : Similar to <code class="literal"> QUANTILE_95 </code> , but for the 99th percentile. </li> <li class="listitem"> <code class="literal"> QUANTILE_999 </code> : Similar to <code class="literal"> QUANTILE_95 </code> , but for the 99.9th percentile. </li> </ul> </div> The <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> table contains the following columns. These are neither grouping nor summary columns; they support statement sampling: <a class="indexterm" name="idm46045068856048"> </a> <a class="indexterm" name="idm46045068854976"> </a> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> QUERY_SAMPLE_TEXT </code> A sample SQL statement that produces the digest value in the row. This column enables applications to access, for a given digest value, a statement actually seen by the server that produces that digest. One use for this might be to run <a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement"> <code class="literal"> EXPLAIN </code> </a> on the statement to examine the execution plan for a representative statement associated with a frequently occurring digest. When the <code class="literal"> QUERY_SAMPLE_TEXT </code> column is assigned a value, the <code class="literal"> QUERY_SAMPLE_SEEN </code> and <code class="literal"> QUERY_SAMPLE_TIMER_WAIT </code> columns are assigned values as well. The maximum space available for statement display is 1024 bytes by default. To change this value, set the <a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_sql_text_length"> <code class="literal"> performance_schema_max_sql_text_length </code> </a> system variable at server startup. (Changing this value affects columns in other Performance Schema tables as well. See <a class="xref" href="performance-schema-statement-digests.html" title="29.10 Performance Schema Statement Digests and Sampling"> Section 29.10, “Performance Schema Statement Digests and Sampling” </a> .) For information about statement sampling, see <a class="xref" href="performance-schema-statement-digests.html" title="29.10 Performance Schema Statement Digests and Sampling"> Section 29.10, “Performance Schema Statement Digests and Sampling” </a> . </li> <li class="listitem"> <code class="literal"> QUERY_SAMPLE_SEEN </code> A timestamp indicating when the statement in the <code class="literal"> QUERY_SAMPLE_TEXT </code> column was seen. </li> <li class="listitem"> <code class="literal"> QUERY_SAMPLE_TIMER_WAIT </code> The wait time for the sample statement in the <code class="literal"> QUERY_SAMPLE_TEXT </code> column. </li> </ul> </div> The <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_program </code> </a> table has these additional summary columns: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> COUNT_STATEMENTS </code> , <code class="literal"> SUM_STATEMENTS_WAIT </code> , <code class="literal"> MIN_STATEMENTS_WAIT </code> , <code class="literal"> AVG_STATEMENTS_WAIT </code> , <code class="literal"> MAX_STATEMENTS_WAIT </code> Statistics about nested statements invoked during stored program execution. </li> </ul> </div> The <a class="link" href="performance-schema-prepared-statements-instances-table.html" title="29.12.6.4 The prepared_statements_instances Table"> <code class="literal"> prepared_statements_instances </code> </a> table has these additional summary columns: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> COUNT_EXECUTE </code> , <code class="literal"> SUM_TIMER_EXECUTE </code> , <code class="literal"> MIN_TIMER_EXECUTE </code> , <code class="literal"> AVG_TIMER_EXECUTE </code> , <code class="literal"> MAX_TIMER_EXECUTE </code> Aggregated statistics for executions of the prepared statement. </li> </ul> </div> The statement summary tables have these indexes: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables"> <code class="literal"> events_transactions_summary_by_account_by_event_name </code> </a> : <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> Primary key on ( <code class="literal"> USER </code> , <code class="literal"> HOST </code> , <code class="literal"> EVENT_NAME </code> ) </li> </ul> </div> </li> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> : <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> Primary key on ( <code class="literal"> SCHEMA_NAME </code> , <code class="literal"> DIGEST </code> ) </li> </ul> </div> </li> <li class="listitem"> <a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables"> <code class="literal"> events_transactions_summary_by_host_by_event_name </code> </a> : <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> Primary key on ( <code class="literal"> HOST </code> , <code class="literal"> EVENT_NAME </code> ) </li> </ul> </div> </li> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_program </code> </a> : <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> Primary key on ( <code class="literal"> OBJECT_TYPE </code> , <code class="literal"> OBJECT_SCHEMA </code> , <code class="literal"> OBJECT_NAME </code> ) </li> </ul> </div> </li> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_thread_by_event_name </code> </a> : <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> Primary key on ( <code class="literal"> THREAD_ID </code> , <code class="literal"> EVENT_NAME </code> ) </li> </ul> </div> </li> <li class="listitem"> <a class="link" href="performance-schema-transaction-summary-tables.html" title="29.12.20.5 Transaction Summary Tables"> <code class="literal"> events_transactions_summary_by_user_by_event_name </code> </a> : <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> Primary key on ( <code class="literal"> USER </code> , <code class="literal"> EVENT_NAME </code> ) </li> </ul> </div> </li> <li class="listitem"> <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_global_by_event_name </code> </a> : <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> Primary key on ( <code class="literal"> EVENT_NAME </code> ) </li> </ul> </div> </li> </ul> </div> <a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement"> <code class="literal"> TRUNCATE TABLE </code> </a> is permitted for statement summary tables. It has these effects: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> For <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> , it removes the rows. </li> <li class="listitem"> For other summary tables not aggregated by account, host, or user, truncation resets the summary columns to zero rather than removing rows. </li> <li class="listitem"> For other summary tables aggregated by account, host, or user, truncation removes rows for accounts, hosts, or users with no connections, and resets the summary columns to zero for the remaining rows. </li> </ul> </div> In addition, each statement summary table that is aggregated by account, host, user, or thread is implicitly truncated by truncation of the connection table on which it depends, or truncation of <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_global_by_event_name </code> </a> . For details, see <a class="xref" href="performance-schema-connection-tables.html" title="29.12.8 Performance Schema Connection Tables"> Section 29.12.8, “Performance Schema Connection Tables” </a> . In addition, truncating <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> implicitly truncates <a class="link" href="performance-schema-statement-histogram-summary-tables.html" title="29.12.20.4 Statement Histogram Summary Tables"> <code class="literal"> events_statements_histogram_by_digest </code> </a> , and truncating <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_global_by_event_name </code> </a> implicitly truncates <a class="link" href="performance-schema-statement-histogram-summary-tables.html" title="29.12.20.4 Statement Histogram Summary Tables"> <code class="literal"> events_statements_histogram_global </code> </a> . <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="statement-summary-tables-aggregation"> </a> Statement Digest Aggregation Rules </h5> </div> </div> </div> If the <code class="literal"> statements_digest </code> consumer is enabled, aggregation into <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> occurs as follows when a statement completes. Aggregation is based on the <code class="literal"> DIGEST </code> value computed for the statement. <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> If a <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_digest </code> </a> row already exists with the digest value for the statement that just completed, statistics for the statement are aggregated to that row. The <code class="literal"> LAST_SEEN </code> column is updated to the current time. </li> <li class="listitem"> If no row has the digest value for the statement that just completed, and the table is not full, a new row is created for the statement. The <code class="literal"> FIRST_SEEN </code> and <code class="literal"> LAST_SEEN </code> columns are initialized with the current time. </li> <li class="listitem"> If no row has the statement digest value for the statement that just completed, and the table is full, the statistics for the statement that just completed are added to a special “ catch-all ” row with <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> , which is created if necessary. If the row is created, the <code class="literal"> FIRST_SEEN </code> and <code class="literal"> LAST_SEEN </code> columns are initialized with the current time. Otherwise, the <code class="literal"> LAST_SEEN </code> column is updated with the current time. </li> </ul> </div> The row with <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> is maintained because Performance Schema tables have a maximum size due to memory constraints. The <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> row permits digests that do not match other rows to be counted even if the summary table is full, using a common “ other ” bucket. This row helps you estimate whether the digest summary is representative: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> A <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> row that has a <code class="literal"> COUNT_STAR </code> value that represents 5% of all digests shows that the digest summary table is very representative; the other rows cover 95% of the statements seen. </li> <li class="listitem"> A <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> row that has a <code class="literal"> COUNT_STAR </code> value that represents 50% of all digests shows that the digest summary table is not very representative; the other rows cover only half the statements seen. Most likely the DBA should increase the maximum table size so that more of the rows counted in the <code class="literal"> DIGEST </code> = <code class="literal"> NULL </code> row would be counted using more specific rows instead. By default, the table is autosized, but if this size is too small, set the <a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_digests_size"> <code class="literal"> performance_schema_digests_size </code> </a> system variable to a larger value at server startup. </li> </ul> </div> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="statement-summary-tables-stored-programs"> </a> Stored Program Instrumentation Behavior </h5> </div> </div> </div> For stored program types for which instrumentation is enabled in the <a class="link" href="performance-schema-setup-objects-table.html" title="29.12.2.4 The setup_objects Table"> <code class="literal"> setup_objects </code> </a> table, <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables"> <code class="literal"> events_statements_summary_by_program </code> </a> maintains statistics for stored programs as follows: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> A row is added for an object when it is first used in the server. </li> <li class="listitem"> The row for an object is removed when the object is dropped. </li> <li class="listitem"> Statistics are aggregated in the row for an object as it executes. </li> </ul> </div> See also <a class="xref" href="performance-schema-pre-filtering.html" title="29.4.3 Event Pre-Filtering"> Section 29.4.3, “Event Pre-Filtering” </a> . </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-backup-troubleshooting.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysql-cluster-backup-troubleshooting"> </a> 25.6.8.4 NDB Cluster Backup Troubleshooting </h4> </div> </div> </div> <a class="indexterm" name="idm46045091920160"> </a> <a class="indexterm" name="idm46045091918672"> </a> <a class="indexterm" name="idm46045091917184"> </a> If an error code is returned when issuing a backup request, the most likely cause is insufficient memory or disk space. You should check that there is enough memory allocated for the backup. <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Important </div> If you have set <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-backupdatabuffersize"> <code class="literal"> BackupDataBufferSize </code> </a> and <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-backuplogbuffersize"> <code class="literal"> BackupLogBufferSize </code> </a> and their sum is greater than 4MB, then you must also set <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-backupmemory"> <code class="literal"> BackupMemory </code> </a> as well. </div> You should also make sure that there is sufficient space on the hard drive partition of the backup target. <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> does not support repeatable reads, which can cause problems with the restoration process. Although the backup process is “ hot ” , restoring an NDB Cluster from backup is not a 100% “ hot ” process. This is due to the fact that, for the duration of the restore process, running transactions get nonrepeatable reads from the restored data. This means that the state of the data is inconsistent while the restore is in progress. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/fetching-spatial-data.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="fetching-spatial-data"> </a> 13.4.8 Fetching Spatial Data </h3> </div> </div> </div> Geometry values stored in a table can be fetched in internal format. You can also convert them to WKT or WKB format. <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> Fetching spatial data in internal format: Fetching geometry values using internal format can be useful in table-to-table transfers: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa34993663"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">CREATE TABLE geom2 (g GEOMETRY) SELECT g FROM geom;</code></pre> </div> </li> <li class="listitem"> Fetching spatial data in WKT format: The <a class="link" href="gis-format-conversion-functions.html#function_st-astext"> <code class="literal"> ST_AsText() </code> </a> function converts a geometry from internal format to a WKT string. <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa49038250"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SELECT ST_AsText(g) FROM geom;</code></pre> </div> </li> <li class="listitem"> Fetching spatial data in WKB format: The <a class="link" href="gis-format-conversion-functions.html#function_st-asbinary"> <code class="literal"> ST_AsBinary() </code> </a> function converts a geometry from internal format to a <a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types"> <code class="literal"> BLOB </code> </a> containing the WKB value. <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa39383153"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SELECT ST_AsBinary(g) FROM geom;</code></pre> </div> </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replication-issues.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="mysql-cluster-replication-issues"> </a> 25.7.3 Known Issues in NDB Cluster Replication </h3> </div> </div> </div> <a class="indexterm" name="idm46045086732400"> </a> This section discusses known problems or issues when using replication with NDB Cluster. Loss of connection between source and replica. <a class="indexterm" name="idm46045086729472"> </a> A loss of connection can occur either between the source cluster SQL node and the replica cluster SQL node, or between the source SQL node and the data nodes of the source cluster. In the latter case, this can occur not only as a result of loss of physical connection (for example, a broken network cable), but due to the overflow of data node event buffers; if the SQL node is too slow to respond, it may be dropped by the cluster (this is controllable to some degree by adjusting the <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-maxbufferedepochs"> <code class="literal"> MaxBufferedEpochs </code> </a> and <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-timebetweenepochs"> <code class="literal"> TimeBetweenEpochs </code> </a> configuration parameters). If this occurs, it is entirely possible for new data to be inserted into the source cluster without being recorded in the source SQL node's binary log . For this reason, to guarantee high availability, it is extremely important to maintain a backup replication channel, to monitor the primary channel, and to fail over to the secondary replication channel when necessary to keep the replica cluster synchronized with the source. NDB Cluster is not designed to perform such monitoring on its own; for this, an external application is required. <a class="indexterm" name="idm46045086723264"> </a> <a class="indexterm" name="idm46045086721776"> </a> The source SQL node issues a “ gap ” event when connecting or reconnecting to the source cluster. (A gap event is a type of “ incident event, ” which indicates an incident that occurs that affects the contents of the database but that cannot easily be represented as a set of changes. Examples of incidents are server failures, database resynchronization, some software updates, and some hardware changes.) When the replica encounters a gap in the replication log, it stops with an error message. This message is available in the output of <a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement"> <code class="literal"> SHOW REPLICA STATUS </code> </a> , and indicates that the SQL thread has stopped due to an incident registered in the replication stream, and that manual intervention is required. See <a class="xref" href="mysql-cluster-replication-failover.html" title="25.7.8 Implementing Failover with NDB Cluster Replication"> Section 25.7.8, “Implementing Failover with NDB Cluster Replication” </a> , for more information about what to do in such circumstances. <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Important </div> Because NDB Cluster is not designed on its own to monitor replication status or provide failover, if high availability is a requirement for the replica server or cluster, then you must set up multiple replication lines, monitor the source <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server"> mysqld </a> on the primary replication line, and be prepared fail over to a secondary line if and as necessary. This must be done manually, or possibly by means of a third-party application. For information about implementing this type of setup, see <a class="xref" href="mysql-cluster-replication-two-channels.html" title="25.7.7 Using Two Replication Channels for NDB Cluster Replication"> Section 25.7.7, “Using Two Replication Channels for NDB Cluster Replication” </a> , and <a class="xref" href="mysql-cluster-replication-failover.html" title="25.7.8 Implementing Failover with NDB Cluster Replication"> Section 25.7.8, “Implementing Failover with NDB Cluster Replication” </a> . If you are replicating from a standalone MySQL server to an NDB Cluster, one channel is usually sufficient. </div> Circular replication. <a class="indexterm" name="idm46045086710848"> </a> <a class="indexterm" name="idm46045086709360"> </a> <a class="indexterm" name="idm46045086707872"> </a> NDB Cluster Replication supports circular replication, as shown in the next example. The replication setup involves three NDB Clusters numbered 1, 2, and 3, in which Cluster 1 acts as the replication source for Cluster 2, Cluster 2 acts as the source for Cluster 3, and Cluster 3 acts as the source for Cluster 1, thus completing the circle. Each NDB Cluster has two SQL nodes, with SQL nodes A and B belonging to Cluster 1, SQL nodes C and D belonging to Cluster 2, and SQL nodes E and F belonging to Cluster 3. Circular replication using these clusters is supported as long as the following conditions are met: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> The SQL nodes on all source and replica clusters are the same. </li> <li class="listitem"> All SQL nodes acting as sources and replicas are started with the system variable <a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates"> <code class="literal"> log_replica_updates </code> </a> enabled. </li> </ul> </div> This type of circular replication setup is shown in the following diagram: <div class="figure"> <a name="fig-mysql-cluster-circular-all-sources-replicas"> </a> Figure 25.11 NDB Cluster Circular Replication With All Sources As Replicas <div class="figure-contents"> <div class="mediaobject"> <img alt="Some content is described in the surrounding text. The diagram shows three clusters, each with two nodes. Arrows connecting SQL nodes in different clusters illustrate that all sources are also replicas." src="images/cluster-circular-replication-1.png" style="width: 100%; max-width: 557px;"/> </div> </div> </div> In this scenario, SQL node A in Cluster 1 replicates to SQL node C in Cluster 2; SQL node C replicates to SQL node E in Cluster 3; SQL node E replicates to SQL node A. In other words, the replication line (indicated by the curved arrows in the diagram) directly connects all SQL nodes used as sources and replicas. It should also be possible to set up circular replication in which not all source SQL nodes are also replicas, as shown here: <div class="figure"> <a name="fig-mysql-cluster-circular-not-all-sources-replicas"> </a> Figure 25.12 NDB Cluster Circular Replication Where Not All Sources Are Replicas <div class="figure-contents"> <div class="mediaobject"> <img alt="Some content is described in the surrounding text. The diagram shows three clusters, each with two nodes. Arrows connecting SQL nodes in different clusters illustrate that not all sources are replicas." src="images/cluster-circular-replication-2.png" style="width: 100%; max-width: 542px;"/> </div> </div> </div> In this case, different SQL nodes in each cluster are used as sources and replicas. However, you must not start any of the SQL nodes with the <a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates"> <code class="literal"> log_replica_updates </code> </a> system variable enabled. This type of circular replication scheme for NDB Cluster, in which the line of replication (again indicated by the curved arrows in the diagram) is discontinuous, should be possible, but it should be noted that it has not yet been thoroughly tested and must therefore still be considered experimental. <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> The <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> storage engine uses idempotent execution mode , which suppresses duplicate-key and other errors that otherwise break circular replication of NDB Cluster. This is equivalent to setting the global value of the system variable <a class="link" href="replication-options-replica.html#sysvar_replica_exec_mode"> <code class="literal"> replica_exec_mode </code> </a> to <code class="literal"> IDEMPOTENT </code> , although this is not necessary in NDB Cluster replication, since NDB Cluster sets this variable automatically and ignores any attempts to set it explicitly. </div> NDB Cluster replication and primary keys. <a class="indexterm" name="idm46045086677184"> </a> In the event of a node failure, errors in replication of <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> tables without primary keys can still occur, due to the possibility of duplicate rows being inserted in such cases. For this reason, it is highly recommended that all <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> tables being replicated have explicit primary keys. NDB Cluster Replication and Unique Keys. <a class="indexterm" name="idm46045086671824"> </a> In older versions of NDB Cluster, operations that updated values of unique key columns of <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> tables could result in duplicate-key errors when replicated. This issue is solved for replication between <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> tables by deferring unique key checks until after all table row updates have been performed. Deferring constraints in this way is currently supported only by <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> . Thus, updates of unique keys when replicating from <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> to a different storage engine such as <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine"> <code class="literal"> InnoDB </code> </a> or <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine"> <code class="literal"> MyISAM </code> </a> are still not supported. The problem encountered when replicating without deferred checking of unique key updates can be illustrated using <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> table such as <code class="literal"> t </code> , is created and populated on the source (and transmitted to a replica that does not support deferred unique key updates) as shown here: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa22455322"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">CREATE TABLE t ( p INT PRIMARY KEY, c INT, UNIQUE KEY u (c) ) ENGINE NDB; INSERT INTO t VALUES (1,1), (2,2), (3,3), (4,4), (5,5);</code></pre> </div> The following <a class="link" href="update.html" title="15.2.17 UPDATE Statement"> <code class="literal"> UPDATE </code> </a> statement on <code class="literal"> t </code> succeeds on the source, since the rows affected are processed in the order determined by the <code class="literal"> ORDER BY </code> option, performed over the entire table: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa24553388"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">UPDATE t SET c = c - 1 ORDER BY p;</code></pre> </div> The same statement fails with a duplicate key error or other constraint violation on the replica, because the ordering of the row updates is performed for one partition at a time, rather than for the table as a whole. <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> Every <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> table is implicitly partitioned by key when it is created. See <a class="xref" href="partitioning-key.html" title="26.2.5 KEY Partitioning"> Section 26.2.5, “KEY Partitioning” </a> , for more information. </div> GTIDs not supported. Replication using global transaction IDs is not compatible with the <code class="literal"> NDB </code> storage engine, and is not supported. Enabling GTIDs is likely to cause NDB Cluster Replication to fail. Restarting with --initial. <a class="indexterm" name="idm46045086647744"> </a> Restarting the cluster with the <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_initial"> <code class="option"> --initial </code> </a> option causes the sequence of GCI and epoch numbers to start over from <code class="literal"> 0 </code> . (This is generally true of NDB Cluster and not limited to replication scenarios involving Cluster.) The MySQL servers involved in replication should in this case be restarted. After this, you should use the <a class="link" href="reset-binary-logs-and-gtids.html" title="15.4.1.2 RESET BINARY LOGS AND GTIDS Statement"> <code class="literal"> RESET BINARY LOGS AND GTIDS </code> </a> and <a class="link" href="reset-replica.html" title="15.4.2.3 RESET REPLICA Statement"> <code class="literal"> RESET REPLICA </code> </a> statements to clear the invalid <code class="literal"> ndb_binlog_index </code> and <code class="literal"> ndb_apply_status </code> tables, respectively. <a name="mysql-cluster-replication-ndb-to-non-ndb"> </a> Replication from NDB to other storage engines. It is possible to replicate an <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> table on the source to a table using a different storage engine on the replica, taking into account the restrictions listed here: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> Multi-source and circular replication are not supported (tables on both the source and the replica must use the <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> storage engine for this to work). </li> <li class="listitem"> Using a storage engine which does not perform binary logging for tables on the replica requires special handling. </li> <li class="listitem"> Use of a nontransactional storage engine for tables on the replica also requires special handling. </li> <li class="listitem"> The source <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server"> mysqld </a> must be started with <a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-as-write"> <code class="option"> --ndb-log-update-as-write=0 </code> </a> or <code class="option"> --ndb-log-update-as-write=OFF </code> . </li> </ul> </div> The next few paragraphs provide additional information about each of the issues just described. Multiple sources not supported when replicating NDB to other storage engines. For replication from <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> to a different storage engine, the relationship between the two databases must be one-to-one. This means that bidirectional or circular replication is not supported between NDB Cluster and other storage engines. In addition, it is not possible to configure more than one replication channel when replicating between <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> and a different storage engine. (An NDB Cluster database can simultaneously replicate to multiple NDB Cluster databases.) If the source uses <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> tables, it is still possible to have more than one MySQL Server maintain a binary log of all changes, but for the replica to change sources (fail over), the new source-replica relationship must be explicitly defined on the replica. Replicating NDB tables to a storage engine that does not perform binary logging. <a class="indexterm" name="idm46045086621024"> </a> If you attempt to replicate from an NDB Cluster to a replica that uses a storage engine that does not handle its own binary logging, the replication process aborts with the error Binary logging not possible ... Statement cannot be written atomically since more than one engine involved and at least one engine is self-logging (Error 1595 ). It is possible to work around this issue in one of the following ways: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> Turn off binary logging on the replica. This can be accomplished by setting <a class="link" href="replication-options-binary-log.html#sysvar_sql_log_bin"> <code class="literal"> sql_log_bin = 0 </code> </a> . </li> <li class="listitem"> Change the storage engine used for the mysql.ndb_apply_status table. Causing this table to use an engine that does not handle its own binary logging can also eliminate the conflict. This can be done by issuing a statement such as <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement"> <code class="literal"> ALTER TABLE mysql.ndb_apply_status ENGINE=MyISAM </code> </a> on the replica. It is safe to do this when using a storage engine other than <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> on the replica, since you do not need to worry about keeping multiple replicas synchronized. </li> <li class="listitem"> Filter out changes to the mysql.ndb_apply_status table on the replica. This can be done by starting the replica with <a class="link" href="replication-options-replica.html#option_mysqld_replicate-ignore-table"> <code class="option"> --replicate-ignore-table=mysql.ndb_apply_status </code> </a> . If you need for other tables to be ignored by replication, you might wish to use an appropriate <a class="link" href="replication-options-replica.html#option_mysqld_replicate-wild-ignore-table"> <code class="option"> --replicate-wild-ignore-table </code> </a> option instead. </li> </ul> </div> <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Important </div> You should not disable replication or binary logging of <code class="literal"> mysql.ndb_apply_status </code> or change the storage engine used for this table when replicating from one NDB Cluster to another. See <a class="xref" href="mysql-cluster-replication-issues.html#mysql-cluster-replication-issues-filtering" title="Replication and binary log filtering rules with replication between NDB Clusters"> Replication and binary log filtering rules with replication between NDB Clusters </a> , for details. </div> <a name="mysql-cluster-replication-ndb-to-nontransactional"> </a> Replication from NDB to a nontransactional storage engine. When replicating from <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> to a nontransactional storage engine such as <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine"> <code class="literal"> MyISAM </code> </a> , you may encounter unnecessary duplicate key errors when replicating <a class="link" href="insert-on-duplicate.html" title="15.2.7.2 INSERT ... ON DUPLICATE KEY UPDATE Statement"> <code class="literal"> INSERT ... ON DUPLICATE KEY UPDATE </code> </a> statements. You can suppress these by using <a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-as-write"> <code class="option"> --ndb-log-update-as-write=0 </code> </a> , which forces updates to be logged as writes, rather than as updates. <a name="mysql-cluster-replication-issues-tde"> </a> NDB Replication and File System Encryption (TDE). The use of an encrypted filesystem does not have any effect on NDB Replication. All of the following scenarios are supported: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> Replication of an NDB Cluster having an encrypted file system to an NDB Cluster whose file system is not encrypted. </li> <li class="listitem"> Replication of an NDB Cluster whose file system is not encrypted to an NDB Cluster whose file system is encrypted. </li> <li class="listitem"> Replication of an NDB Cluster whose file system is encrypted to a standalone MySQL server using <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine"> <code class="literal"> InnoDB </code> </a> tables which are not encrypted. </li> <li class="listitem"> Replication of an NDB Cluster with an unencrypted file system to a standalone MySQL server using <code class="literal"> InnoDB </code> tables with file sytem encryption. </li> </ul> </div> <a name="mysql-cluster-replication-issues-filtering"> </a> Replication and binary log filtering rules with replication between NDB Clusters. If you are using any of the options <code class="option"> --replicate-do-* </code> , <code class="option"> --replicate-ignore-* </code> , <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db </code> </a> , or <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db"> <code class="option"> --binlog-ignore-db </code> </a> to filter databases or tables being replicated, you must take care not to block replication or binary logging of the <code class="literal"> mysql.ndb_apply_status </code> , which is required for replication between NDB Clusters to operate properly. In particular, you must keep in mind the following: <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> Using <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-db"> <code class="option"> --replicate-do-db= <code> db_name </code> </code> </a> (and no other <code class="option"> --replicate-do-* </code> or <code class="option"> --replicate-ignore-* </code> options) means that only tables in database <code> db_name </code> are replicated. In this case, you should also use <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-db"> <code class="option"> --replicate-do-db=mysql </code> </a> , <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db=mysql </code> </a> , or <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-table"> <code class="option"> --replicate-do-table=mysql.ndb_apply_status </code> </a> to ensure that <code class="literal"> mysql.ndb_apply_status </code> is populated on replicas. Using <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db= <code> db_name </code> </code> </a> (and no other <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db </code> </a> options) means that changes only to tables in database <code> db_name </code> are written to the binary log. In this case, you should also use <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-db"> <code class="option"> --replicate-do-db=mysql </code> </a> , <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db=mysql </code> </a> , or <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-table"> <code class="option"> --replicate-do-table=mysql.ndb_apply_status </code> </a> to ensure that <code class="literal"> mysql.ndb_apply_status </code> is populated on replicas. </li> <li class="listitem"> Using <a class="link" href="replication-options-replica.html#option_mysqld_replicate-ignore-db"> <code class="option"> --replicate-ignore-db=mysql </code> </a> means that no tables in the <code class="literal"> mysql </code> database are replicated. In this case, you should also use <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-table"> <code class="option"> --replicate-do-table=mysql.ndb_apply_status </code> </a> to ensure that <code class="literal"> mysql.ndb_apply_status </code> is replicated. Using <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db"> <code class="option"> --binlog-ignore-db=mysql </code> </a> means that no changes to tables in the <code class="literal"> mysql </code> database are written to the binary log. In this case, you should also use <a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-table"> <code class="option"> --replicate-do-table=mysql.ndb_apply_status </code> </a> to ensure that <code class="literal"> mysql.ndb_apply_status </code> is replicated. </li> </ol> </div> You should also remember that each replication rule requires the following: <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> Its own <code class="option"> --replicate-do-* </code> or <code class="option"> --replicate-ignore-* </code> option, and that multiple rules cannot be expressed in a single replication filtering option. For information about these rules, see <a class="xref" href="replication-options.html" title="19.1.6 Replication and Binary Logging Options and Variables"> Section 19.1.6, “Replication and Binary Logging Options and Variables” </a> . </li> <li class="listitem"> Its own <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db"> <code class="option"> --binlog-do-db </code> </a> or <a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db"> <code class="option"> --binlog-ignore-db </code> </a> option, and that multiple rules cannot be expressed in a single binary log filtering option. For information about these rules, see <a class="xref" href="binary-log.html" title="7.4.4 The Binary Log"> Section 7.4.4, “The Binary Log” </a> . </li> </ol> </div> If you are replicating an NDB Cluster to a replica that uses a storage engine other than <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDB </code> </a> , the considerations just given previously may not apply, as discussed elsewhere in this section. <a name="mysql-cluster-replication-ipv6"> </a> NDB Cluster Replication and IPv6. All types of NDB Cluster nodes support IPv6 in NDB 8.4; this includes management nodes, data nodes, and API or SQL nodes. <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> In NDB 8.4, you can disable IPv6 support in the Linux kernel if you do not intend to use IPv6 addressing for any NDB Cluster nodes. </div> Attribute promotion and demotion. NDB Cluster Replication includes support for attribute promotion and demotion. The implementation of the latter distinguishes between lossy and non-lossy type conversions, and their use on the replica can be controlled by setting the global value of the system variable <a class="link" href="replication-options-replica.html#sysvar_replica_type_conversions"> <code class="literal"> replica_type_conversions </code> </a> . For more information about attribute promotion and demotion in NDB Cluster, see <a class="xref" href="replication-features-differing-tables.html#replication-features-attribute-promotion" title="Row-based replication: attribute promotion and demotion"> Row-based replication: attribute promotion and demotion </a> . <code class="literal"> NDB </code> , unlike <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine"> <code class="literal"> InnoDB </code> </a> or <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine"> <code class="literal"> MyISAM </code> </a> , does not write changes to virtual columns to the binary log; however, this has no detrimental effects on NDB Cluster Replication or replication between <code class="literal"> NDB </code> and other storage engines. Changes to stored generated columns are logged. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/telemetry-metrics.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="telemetry-metrics"> </a> 35.4 OpenTelemetry Metrics </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <a href="telemetry-metrics-configuration.html"> 35.4.1 Configuring Metrics Telemetry </a> </dt> <dt> <a href="telemetry-metrics-meters.html"> 35.4.2 Server Meters </a> </dt> <dt> <a href="telemetry-metrics-meter-metrics.html"> 35.4.3 Server Metrics </a> </dt> </dl> </div> The Server Telemetry Metrics Service and the Server Metrics Instrument Service enable you to register and query telemetry meters, metrics, and metric measurements, in order to periodically export these measurements using the OpenTelemetry protocol. For more information on these services, see Server Telemetry Metrics Service and the Server Metrics Instrument Service documentation in the MySQL Server Doxygen Documentation. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-hwinfo.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysql-cluster-ndbinfo-hwinfo"> </a> 25.6.17.39 The ndbinfo hwinfo Table </h4> </div> </div> </div> <a class="indexterm" name="idm46045089150512"> </a> The <code class="literal"> hwinfo </code> table provides information about the hardware on which a given data node executes. The <code class="literal"> hwinfo </code> table contains the following columns: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> node_id </code> Node ID </li> <li class="listitem"> <code class="literal"> cpu_cnt_max </code> Number of processors on this host </li> <li class="listitem"> <code class="literal"> cpu_cnt </code> Number of processors available to this node </li> <li class="listitem"> <code class="literal"> num_cpu_cores </code> Number of CPU cores on this host </li> <li class="listitem"> <code class="literal"> num_cpu_sockets </code> Number of CPU sockets on this host </li> <li class="listitem"> <code class="literal"> HW_memory_size </code> Amount of memory available on this host </li> <li class="listitem"> <code class="literal"> model_name </code> CPU model name </li> </ul> </div> <h5> <a name="idm46045089132880"> </a> Notes </h5> The <code class="literal"> hwinfo </code> table is available on all operating systems supported by <code class="literal"> NDB </code> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/what-is-crashing.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="what-is-crashing"> </a> B.3.1 How to Determine What Is Causing a Problem </h3> </div> </div> </div> When you run into a problem, the first thing you should do is to find out which program or piece of equipment is causing it: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> If you have one of the following symptoms, then it is probably a hardware problems (such as memory, motherboard, CPU, or hard disk) or kernel problem: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> The keyboard does not work. This can normally be checked by pressing the Caps Lock key. If the Caps Lock light does not change, you have to replace your keyboard. (Before doing this, you should try to restart your computer and check all cables to the keyboard.) </li> <li class="listitem"> The mouse pointer does not move. </li> <li class="listitem"> The machine does not answer to a remote machine's pings. </li> <li class="listitem"> Other programs that are not related to MySQL do not behave correctly. </li> <li class="listitem"> Your system restarted unexpectedly. (A faulty user-level program should never be able to take down your system.) </li> </ul> </div> In this case, you should start by checking all your cables and run some diagnostic tool to check your hardware! You should also check whether there are any patches, updates, or service packs for your operating system that could likely solve your problem. Check also that all your libraries (such as <code class="literal"> glibc </code> ) are up to date. It is always good to use a machine with ECC memory to discover memory problems early. </li> <li class="listitem"> If your keyboard is locked up, you may be able to recover by logging in to your machine from another machine and executing <code class="literal"> kbd_mode -a </code> . </li> <li class="listitem"> Please examine your system log file ( <code class="filename"> /var/log/messages </code> or similar) for reasons for your problem. If you think the problem is in MySQL, you should also examine MySQL's log files. See <a class="xref" href="server-logs.html" title="7.4 MySQL Server Logs"> Section 7.4, “MySQL Server Logs” </a> . </li> <li class="listitem"> If you do not think you have hardware problems, you should try to find out which program is causing problems. Try using top , ps , Task Manager, or some similar program, to check which program is taking all CPU or is locking the machine. </li> <li class="listitem"> Use top , df , or a similar program to check whether you are out of memory, disk space, file descriptors, or some other critical resource. </li> <li class="listitem"> If the problem is some runaway process, you can always try to kill it. If it does not want to die, there is probably a bug in the operating system. </li> </ul> </div> If you have examined all other possibilities and concluded that the MySQL server or a MySQL client is causing the problem, it is time to create a bug report, see <a class="xref" href="bug-reports.html" title="1.6 How to Report Bugs or Problems"> Section 1.6, “How to Report Bugs or Problems” </a> . In the bug report, try to give a complete description of how the system is behaving and what you think is happening. Also state why you think that MySQL is causing the problem. Take into consideration all the situations described in this chapter. State any problems exactly how they appear when you examine your system. Use the “ copy and paste ” method for any output and error messages from programs and log files. Try to describe in detail which program is not working and all symptoms you see. We have in the past received many bug reports that state only “ the system does not work. ” This provides us with no information about what could be the problem. If a program fails, it is always useful to know the following information: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> Has the program in question made a segmentation fault (did it dump core)? </li> <li class="listitem"> Is the program taking up all available CPU time? Check with top . Let the program run for a while, it may simply be evaluating something computationally intensive. </li> <li class="listitem"> If the <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server"> mysqld </a> server is causing problems, can you get any response from it with <a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program"> mysqladmin -u root ping </a> or <a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program"> mysqladmin -u root processlist </a> ? </li> <li class="listitem"> What does a client program say when you try to connect to the MySQL server? (Try with <a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client"> mysql </a> , for example.) Does the client jam? Do you get any output from the program? </li> </ul> </div> When sending a bug report, you should follow the outline described in <a class="xref" href="bug-reports.html" title="1.6 How to Report Bugs or Problems"> Section 1.6, “How to Report Bugs or Problems” </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/gis-general-property-functions.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="gis-general-property-functions"> </a> 14.16.7.1 General Geometry Property Functions </h4> </div> </div> </div> The functions listed in this section do not restrict their argument and accept a geometry value of any type. Unless otherwise specified, functions in this section handle their geometry arguments as follows: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> If any argument is <code class="literal"> NULL </code> , the return value is <code class="literal"> NULL </code> . </li> <li class="listitem"> If any geometry argument is not a syntactically well-formed geometry, an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_gis_invalid_data" target="_top"> <code class="literal"> ER_GIS_INVALID_DATA </code> </a> error occurs. </li> <li class="listitem"> If any geometry argument is a syntactically well-formed geometry in an undefined spatial reference system (SRS), an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_srs_not_found" target="_top"> <code class="literal"> ER_SRS_NOT_FOUND </code> </a> error occurs. </li> <li class="listitem"> If any SRID argument is not within the range of a 32-bit unsigned integer, an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_data_out_of_range" target="_top"> <code class="literal"> ER_DATA_OUT_OF_RANGE </code> </a> error occurs. </li> <li class="listitem"> If any SRID argument refers to an undefined SRS, an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_srs_not_found" target="_top"> <code class="literal"> ER_SRS_NOT_FOUND </code> </a> error occurs. </li> <li class="listitem"> Otherwise, the return value is non- <code class="literal"> NULL </code> . </li> </ul> </div> These functions are available for obtaining geometry properties: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <a name="function_st-dimension"> </a> <a class="link" href="gis-general-property-functions.html#function_st-dimension"> <code class="literal"> ST_Dimension( <code> g </code> ) </code> </a> <a class="indexterm" name="idm46045197547632"> </a> Returns the inherent dimension of the geometry value <code> g </code> . The dimension can be −1, 0, 1, or 2. The meaning of these values is given in <a class="xref" href="gis-class-geometry.html" title="13.4.2.2 Geometry Class"> Section 13.4.2.2, “Geometry Class” </a> . <a class="link" href="gis-general-property-functions.html#function_st-dimension"> <code class="literal"> ST_Dimension() </code> </a> handles its arguments as described in the introduction to this section. <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa54369554"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT ST_Dimension(ST_GeomFromText('LineString(1 1,2 2)')); +------------------------------------------------------+ | ST_Dimension(ST_GeomFromText('LineString(1 1,2 2)')) | +------------------------------------------------------+ | 1 | +------------------------------------------------------+</code></pre> </div> </li> <li class="listitem"> <a name="function_st-envelope"> </a> <a class="link" href="gis-general-property-functions.html#function_st-envelope"> <code class="literal"> ST_Envelope( <code> g </code> ) </code> </a> <a class="indexterm" name="idm46045197535264"> </a> Returns the minimum bounding rectangle (MBR) for the geometry value <code> g </code> . The result is returned as a <code class="literal"> Polygon </code> value that is defined by the corner points of the bounding box: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa23466958"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">POLYGON((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY))</code></pre> </div> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46018837"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT ST_AsText(ST_Envelope(ST_GeomFromText('LineString(1 1,2 2)'))); +----------------------------------------------------------------+ | ST_AsText(ST_Envelope(ST_GeomFromText('LineString(1 1,2 2)'))) | +----------------------------------------------------------------+ | POLYGON((1 1,2 1,2 2,1 2,1 1)) | +----------------------------------------------------------------+</code></pre> </div> If the argument is a point or a vertical or horizontal line segment, <a class="link" href="gis-general-property-functions.html#function_st-envelope"> <code class="literal"> ST_Envelope() </code> </a> returns the point or the line segment as its MBR rather than returning an invalid polygon: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa82926961"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT ST_AsText(ST_Envelope(ST_GeomFromText('LineString(1 1,1 2)'))); +----------------------------------------------------------------+ | ST_AsText(ST_Envelope(ST_GeomFromText('LineString(1 1,1 2)'))) | +----------------------------------------------------------------+ | LINESTRING(1 1,1 2) | +----------------------------------------------------------------+</code></pre> </div> <a class="link" href="gis-general-property-functions.html#function_st-envelope"> <code class="literal"> ST_Envelope() </code> </a> handles its arguments as described in the introduction to this section, with this exception: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> If the geometry has an SRID value for a geographic spatial reference system (SRS), an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_not_implemented_for_geographic_srs" target="_top"> <code class="literal"> ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS </code> </a> error occurs. </li> </ul> </div> </li> <li class="listitem"> <a name="function_st-geometrytype"> </a> <a class="link" href="gis-general-property-functions.html#function_st-geometrytype"> <code class="literal"> ST_GeometryType( <code> g </code> ) </code> </a> <a class="indexterm" name="idm46045197515872"> </a> Returns a binary string indicating the name of the geometry type of which the geometry instance <code> g </code> is a member. The name corresponds to one of the instantiable <code class="literal"> Geometry </code> subclasses. <a class="link" href="gis-general-property-functions.html#function_st-geometrytype"> <code class="literal"> ST_GeometryType() </code> </a> handles its arguments as described in the introduction to this section. <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa1317378"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT ST_GeometryType(ST_GeomFromText('POINT(1 1)')); +------------------------------------------------+ | ST_GeometryType(ST_GeomFromText('POINT(1 1)')) | +------------------------------------------------+ | POINT | +------------------------------------------------+</code></pre> </div> </li> <li class="listitem"> <a name="function_st-isempty"> </a> <a class="link" href="gis-general-property-functions.html#function_st-isempty"> <code class="literal"> ST_IsEmpty( <code> g </code> ) </code> </a> <a class="indexterm" name="idm46045197503600"> </a> This function is a placeholder that returns 1 for an empty geometry collection value or 0 otherwise. The only valid empty geometry is represented in the form of an empty geometry collection value. MySQL does not support GIS <code class="literal"> EMPTY </code> values such as <code class="literal"> POINT EMPTY </code> . <a class="link" href="gis-general-property-functions.html#function_st-isempty"> <code class="literal"> ST_IsEmpty() </code> </a> handles its arguments as described in the introduction to this section. </li> <li class="listitem"> <a name="function_st-issimple"> </a> <a class="link" href="gis-general-property-functions.html#function_st-issimple"> <code class="literal"> ST_IsSimple( <code> g </code> ) </code> </a> <a class="indexterm" name="idm46045197493008"> </a> Returns 1 if the geometry value <code> g </code> is simple according to the ISO SQL/MM Part 3: Spatial standard. <a class="link" href="gis-general-property-functions.html#function_st-issimple"> <code class="literal"> ST_IsSimple() </code> </a> returns 0 if the argument is not simple. The descriptions of the instantiable geometric classes given under <a class="xref" href="opengis-geometry-model.html" title="13.4.2 The OpenGIS Geometry Model"> Section 13.4.2, “The OpenGIS Geometry Model” </a> include the specific conditions that cause class instances to be classified as not simple. <a class="link" href="gis-general-property-functions.html#function_st-issimple"> <code class="literal"> ST_IsSimple() </code> </a> handles its arguments as described in the introduction to this section, with this exception: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> If the geometry has a geographic SRS with a longitude or latitude that is out of range, an error occurs: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: square; "> <li class="listitem"> If a longitude value is not in the range (−180, 180], an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_geometry_param_longitude_out_of_range" target="_top"> <code class="literal"> ER_GEOMETRY_PARAM_LONGITUDE_OUT_OF_RANGE </code> </a> error occurs. </li> <li class="listitem"> If a latitude value is not in the range [−90, 90], an <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_geometry_param_latitude_out_of_range" target="_top"> <code class="literal"> ER_GEOMETRY_PARAM_LATITUDE_OUT_OF_RANGE </code> </a> error occurs. </li> </ul> </div> Ranges shown are in degrees. The exact range limits deviate slightly due to floating-point arithmetic. </li> </ul> </div> </li> <li class="listitem"> <a name="function_st-srid"> </a> <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID( <code> g </code> [, <code> srid </code> ]) </code> </a> <a class="indexterm" name="idm46045197473632"> </a> With a single argument representing a valid geometry object <code> g </code> , <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> returns an integer indicating the ID of the spatial reference system (SRS) associated with <code> g </code> . With the optional second argument representing a valid SRID value, <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> returns an object with the same type as its first argument with an SRID value equal to the second argument. This only sets the SRID value of the object; it does not perform any transformation of coordinate values. <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> handles its arguments as described in the introduction to this section, with this exception: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> For the single-argument syntax, <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> returns the geometry SRID even if it refers to an undefined SRS. An <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_srs_not_found" target="_top"> <code class="literal"> ER_SRS_NOT_FOUND </code> </a> error does not occur. </li> </ul> </div> <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID( <code> g </code> , <code> target_srid </code> ) </code> </a> and <a class="link" href="spatial-operator-functions.html#function_st-transform"> <code class="literal"> ST_Transform( <code> g </code> , <code> target_srid </code> ) </code> </a> differ as follows: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> changes the geometry SRID value without transforming its coordinates. </li> <li class="listitem"> <a class="link" href="spatial-operator-functions.html#function_st-transform"> <code class="literal"> ST_Transform() </code> </a> transforms the geometry coordinates in addition to changing its SRID value. </li> </ul> </div> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa74861556"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SET @g = ST_GeomFromText('LineString(1 1,2 2)', 0); mysql> SELECT ST_SRID(@g); +-------------+ | ST_SRID(@g) | +-------------+ | 0 | +-------------+ mysql> SET @g = ST_SRID(@g, 4326); mysql> SELECT ST_SRID(@g); +-------------+ | ST_SRID(@g) | +-------------+ | 4326 | +-------------+</code></pre> </div> It is possible to create a geometry in a particular SRID by passing to <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> the result of one of the MySQL-specific functions for creating spatial values, along with an SRID value. For example: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa77323920"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SET @g1 = ST_SRID(Point(1, 1), 4326);</code></pre> </div> However, that method creates the geometry in SRID 0, then casts it to SRID 4326 (WGS 84). A preferable alternative is to create the geometry with the correct spatial reference system to begin with. For example: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa77913484"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SET @g1 = ST_PointFromText('POINT(1 1)', 4326); SET @g1 = ST_GeomFromText('POINT(1 1)', 4326);</code></pre> </div> The two-argument form of <a class="link" href="gis-general-property-functions.html#function_st-srid"> <code class="literal"> ST_SRID() </code> </a> is useful for tasks such as correcting or changing the SRS of geometries that have an incorrect SRID. </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/savepoint.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="savepoint"> </a> 15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements </h3> </div> </div> </div> <a class="indexterm" name="idm46045178627760"> </a> <a class="indexterm" name="idm46045178626720"> </a> <a class="indexterm" name="idm46045178625648"> </a> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa66696333"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">SAVEPOINT identifier ROLLBACK [WORK] TO [SAVEPOINT] identifier RELEASE SAVEPOINT identifier</code></pre> </div> <code class="literal"> InnoDB </code> supports the SQL statements <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> SAVEPOINT </code> </a> , <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> ROLLBACK TO SAVEPOINT </code> </a> , <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> RELEASE SAVEPOINT </code> </a> and the optional <code class="literal"> WORK </code> keyword for <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements"> <code class="literal"> ROLLBACK </code> </a> . The <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> SAVEPOINT </code> </a> statement sets a named transaction savepoint with a name of <code> identifier </code> . If the current transaction has a savepoint with the same name, the old savepoint is deleted and a new one is set. The <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> ROLLBACK TO SAVEPOINT </code> </a> statement rolls back a transaction to the named savepoint without terminating the transaction. Modifications that the current transaction made to rows after the savepoint was set are undone in the rollback, but <code class="literal"> InnoDB </code> does not release the row locks that were stored in memory after the savepoint. (For a new inserted row, the lock information is carried by the transaction ID stored in the row; the lock is not separately stored in memory. In this case, the row lock is released in the undo.) Savepoints that were set at a later time than the named savepoint are deleted. If the <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> ROLLBACK TO SAVEPOINT </code> </a> statement returns the following error, it means that no savepoint with the specified name exists: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-none"><div class="docs-select-all right" id="sa17695036"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-none">ERROR 1305 (42000): SAVEPOINT identifier does not exist</code></pre> </div> The <a class="link" href="savepoint.html" title="15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements"> <code class="literal"> RELEASE SAVEPOINT </code> </a> statement removes the named savepoint from the set of savepoints of the current transaction. No commit or rollback occurs. It is an error if the savepoint does not exist. All savepoints of the current transaction are deleted if you execute a <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements"> <code class="literal"> COMMIT </code> </a> , or a <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements"> <code class="literal"> ROLLBACK </code> </a> that does not name a savepoint. A new savepoint level is created when a stored function is invoked or a trigger is activated. The savepoints on previous levels become unavailable and thus do not conflict with savepoints on the new level. When the function or trigger terminates, any savepoints it created are released and the previous savepoint level is restored. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-quick.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="mysql-cluster-quick"> </a> 25.4.1 Quick Test Setup of NDB Cluster </h3> </div> </div> </div> <a class="indexterm" name="idm46045122003648"> </a> <a class="indexterm" name="idm46045122002192"> </a> <a class="indexterm" name="idm46045122000704"> </a> To familiarize you with the basics, we describe the simplest possible configuration for a functional NDB Cluster. After this, you should be able to design your desired setup from the information provided in the other relevant sections of this chapter. First, you need to create a configuration directory such as <code class="filename"> /var/lib/mysql-cluster </code> , by executing the following command as the system <code class="literal"> root </code> user: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa96211790"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-terminal">$> mkdir /var/lib/mysql-cluster</code></pre> </div> In this directory, create a file named <code class="filename"> config.ini </code> that contains the following information. Substitute appropriate values for <code class="literal"> HostName </code> and <code class="literal"> DataDir </code> as necessary for your system. <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa82302769"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-ini"># file "config.ini" - showing minimal setup consisting of 1 data node, # 1 management server, and 3 MySQL servers. # The empty default sections are not required, and are shown only for # the sake of completeness. # Data nodes must provide a hostname but MySQL Servers are not required # to do so. # If you do not know the hostname for your machine, use localhost. # The DataDir parameter also has a default value, but it is recommended to # set it explicitly. # [api] and [mgm] are aliases for [mysqld] and [ndb_mgmd], respectively. [ndbd default] NoOfReplicas= 1 [mysqld default] [ndb_mgmd default] [tcp default] [ndb_mgmd] HostName= myhost.example.com [ndbd] HostName= myhost.example.com DataDir= /var/lib/mysql-cluster [mysqld] [mysqld] [mysqld]</code></pre> </div> You can now start the <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> management server. By default, it attempts to read the <code class="filename"> config.ini </code> file in its current working directory, so change location into the directory where the file is located and then invoke <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> : <div class="copytoclipboard-wrapper"> <pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa70209928"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-terminal">$> cd /var/lib/mysql-cluster $> ndb_mgmd</code></pre> </div> Then start a single data node by running <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> ndbd </a> : <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa39743877"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-terminal">$> ndbd</code></pre> </div> By default, <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> ndbd </a> looks for the management server at <code class="literal"> localhost </code> on port 1186. <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Note </div> If you have installed MySQL from a binary tarball, you must to specify the path of the <a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon"> ndb_mgmd </a> and <a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon"> ndbd </a> servers explicitly. (Normally, these can be found in <code class="filename"> /usr/local/mysql/bin </code> .) </div> Finally, change location to the MySQL data directory (usually <code class="filename"> /var/lib/mysql </code> or <code class="filename"> /usr/local/mysql/data </code> ), and make sure that the <code class="filename"> my.cnf </code> file contains the option necessary to enable the NDB storage engine: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa43644783"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-ini">[mysqld] ndbcluster</code></pre> </div> You can now start the MySQL server as usual: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa11789097"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-terminal">$> mysqld_safe --user=mysql &</code></pre> </div> Wait a moment to make sure the MySQL server is running properly. If you see the notice <code class="literal"> mysql ended </code> , check the server's <code class="filename"> .err </code> file to find out what went wrong. If all has gone well so far, you now can start using the cluster. Connect to the server and verify that the <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDBCLUSTER </code> </a> storage engine is enabled: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36151102"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">$> mysql Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 1 to server version: 8.4.3 Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> SHOW ENGINES\G ... *************************** 12. row *************************** Engine: NDBCLUSTER Support: YES Comment: Clustered, fault-tolerant, memory-based tables *************************** 13. row *************************** Engine: NDB Support: YES Comment: Alias for NDBCLUSTER ...</code></pre> </div> The row numbers shown in the preceding example output may be different from those shown on your system, depending upon how your server is configured. Try to create an <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4"> <code class="literal"> NDBCLUSTER </code> </a> table: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16444736"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">$> mysql mysql> USE test; Database changed mysql> CREATE TABLE ctest (i INT) ENGINE=NDBCLUSTER; Query OK, 0 rows affected (0.09 sec) mysql> SHOW CREATE TABLE ctest \G *************************** 1. row *************************** Table: ctest Create Table: CREATE TABLE `ctest` ( `i` int(11) default NULL ) ENGINE=ndbcluster DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci 1 row in set (0.00 sec)</code></pre> </div> To check that your nodes were set up properly, start the management client: <div class="copytoclipboard-wrapper"> <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa11350256"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-terminal">$> ndb_mgm</code></pre> </div> <a class="indexterm" name="idm46045121953184"> </a> Use the SHOW command from within the management client to obtain a report on the cluster's status: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ndbmgm"><div class="docs-select-all right" id="sa85074722"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-ndbmgm">ndb_mgm> SHOW Cluster Configuration --------------------- [ndbd(NDB)] 1 node(s) id=2 @127.0.0.1 (Version: 8.4.0-ndb-8.4.0, Nodegroup: 0, *) [ndb_mgmd(MGM)] 1 node(s) id=1 @127.0.0.1 (Version: 8.4.0-ndb-8.4.0) [mysqld(API)] 3 node(s) id=3 @127.0.0.1 (Version: 8.4.0-ndb-8.4.0) id=4 (not connected, accepting connect from any host) id=5 (not connected, accepting connect from any host)</code></pre> </div> At this point, you have successfully set up a working NDB Cluster. You can now store data in the cluster by using any table created with <code class="literal"> ENGINE=NDBCLUSTER </code> or its alias <code class="literal"> ENGINE=NDB </code> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-tde-setup.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysql-cluster-tde-setup"> </a> 25.6.14.1 NDB File System Encryption Setup and Usage </h4> </div> </div> </div> Encryption of file system : To enable encryption of a previously unencrypted file system, the following steps are required: <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> Set the required data node parameters in the <code class="literal"> [ndbd default] </code> section of the <code class="filename"> config.ini </code> file, as shown here: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa24733928"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-ini">[ndbd default] EncryptedFileSystem= 1</code></pre> </div> These parameters must be set as shown on all data nodes. </li> <li class="listitem"> Start the management server with either <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_initial"> <code class="option"> --initial </code> </a> or <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_reload"> <code class="option"> --reload </code> </a> to cause it to read the updated configuration file. </li> <li class="listitem"> Perform a rolling initial start (or restart) of all the data nodes (see <a class="xref" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster"> Section 25.6.5, “Performing a Rolling Restart of an NDB Cluster” </a> ): Start each data node with <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_initial"> <code class="option"> --initial </code> </a> ; in addition, supply either of the options <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_filesystem-password"> <code class="option"> --filesystem-password </code> </a> or <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_filesystem-password-from-stdin"> <code class="option"> --filesystem-password-from-stdin </code> </a> , plus a password, to each data node process. When you supply the password on the command line, a warning is shown, similar to this one: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa67561162"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-terminal">> ndbmtd -c 127.0.0.1 --filesystem-password=ndbsecret ndbmtd: [Warning] Using a password on the command line interface can be insecure. 2022-08-22 16:17:58 [ndbd] INFO -- Angel connected to '127.0.0.1:1186' 2022-08-22 16:17:58 [ndbd] INFO -- Angel allocated nodeid: 5</code></pre> </div> <code class="option"> --filesystem-password </code> can accept the password form a file, <code class="literal"> tty </code> , or <code class="literal"> stdin </code> ; <code class="option"> --filesystem-password-from-stdin </code> accepts the password from <code class="literal"> stdin </code> only. The latter protects the password from exposure on the process command line or in the file system, and allows for the possibility of passing it from another secure application. You can also place the password in a <code class="filename"> my.cnf </code> file that can be read by the data node process, but not by other users of the system. Using the same password as in the previous example, the relevant portion of the file should look like this: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa11886616"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-ini">[ndbd] filesystem-password=ndbsecret</code></pre> </div> You can also prompt the user starting the data node process to supply the encryption password when doing so, by using the <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_filesystem-password-from-stdin"> <code class="option"> --filesystem-password-from-stdin </code> </a> option in the <code class="filename"> my.cnf </code> file instead, like this: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa18566545"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-ini">[ndbd] filesystem-password-from-stdin</code></pre> </div> In this case, the user is prompted for the password when starting the data node process, as shown here: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-ndbmgm"><div class="docs-select-all right" id="sa18121554"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-ndbmgm">> ndbmtd -c 127.0.0.1 Enter filesystem password: ********* 2022-08-22 16:36:00 [ndbd] INFO -- Angel connected to '127.0.0.1:1186' 2022-08-22 16:36:00 [ndbd] INFO -- Angel allocated nodeid: 5 ></code></pre> </div> Regardless of the method used, the format of the encryption password is the same as that used for passwords for encrypted backups (see <a class="xref" href="mysql-cluster-backup-using-management-client.html" title="25.6.8.2 Using The NDB Cluster Management Client to Create a Backup"> Section 25.6.8.2, “Using The NDB Cluster Management Client to Create a Backup” </a> ); the password must be supplied when starting each data node process; otherwise the data node process cannot start. This is indicated by the following message in the data node log: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa57750876"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-terminal">> tail -n2 ndb_5_out.log 2022-08-22 16:08:30 [ndbd] INFO -- Data node configured to have encryption but password not provided 2022-08-22 16:08:31 [ndbd] ALERT -- Node 5: Forced node shutdown completed. Occurred during startphase 0.</code></pre> </div> When restarted as just described, each data node clears its on-disk state, and rebuilds it in encrypted form. </li> </ol> </div> Rotation of File system password : To update the encryption password used by the data nodes, perform a rolling initial restart of the data nodes, supplying the new password to each data node when restarting it using <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_filesystem-password"> <code class="option"> --filesystem-password </code> </a> or <a class="link" href="mysql-cluster-programs-ndbd.html#option_ndbd_filesystem-password-from-stdin"> <code class="option"> --filesystem-password-from-stdin </code> </a> . Decryption of file system : To remove encryption from an encrypted file system, do the following: <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> In the <code class="literal"> [ndbd default] </code> section of the <code class="filename"> config.ini </code> file, set <code class="literal"> EncryptedFileSystem = OFF </code> . </li> <li class="listitem"> Restart the management server with <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_initial"> <code class="option"> --initial </code> </a> or <a class="link" href="mysql-cluster-programs-ndb-mgmd.html#option_ndb_mgmd_reload"> <code class="option"> --reload </code> </a> . </li> <li class="listitem"> Perform a rolling initial restart of the data nodes. Do not use any password-related options when restarting the node binaries. When restarted, each data node clears its on-disk state, and rebuilds it in unencrypted form. </li> </ol> </div> To see whether file system encryption is properly configured, you can use a query against the <code class="literal"> ndbinfo </code> <a class="link" href="mysql-cluster-ndbinfo-config-values.html" title="25.6.17.12 The ndbinfo config_values Table"> <code class="literal"> config_values </code> </a> and <a class="link" href="mysql-cluster-ndbinfo-config-params.html" title="25.6.17.11 The ndbinfo config_params Table"> <code class="literal"> config_params </code> </a> tables similar to this one: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30908465"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT v.node_id AS Node, p.param_name AS Parameter, v.config_value AS Value -> FROM ndbinfo.config_values v -> JOIN ndbinfo.config_params p -> ON v.config_param=p.param_number -> WHERE p.param_name='EncryptedFileSystem'; +------+----------------------+-------+ | Node | Parameter | Value | +------+----------------------+-------+ | 5 | EncryptedFileSystem | 1 | | 6 | EncryptedFileSystem | 1 | | 7 | EncryptedFileSystem | 1 | | 8 | EncryptedFileSystem | 1 | +------+----------------------+-------+ 4 rows in set (0.10 sec)</code></pre> </div> Here, <a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-encryptedfilesystem"> <code class="literal"> EncryptedFileSystem </code> </a> is equal to <code class="literal"> 1 </code> on all data nodes, which means that filesystem encryption is enabled for this cluster. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/sys-ps-is-account-enabled.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="sys-ps-is-account-enabled"> </a> 30.4.5.9 The ps_is_account_enabled() Function </h4> </div> </div> </div> <a class="indexterm" name="idm46045060891392"> </a> <a class="indexterm" name="idm46045060889888"> </a> Returns <code class="literal"> YES </code> or <code class="literal"> NO </code> to indicate whether Performance Schema instrumentation for a given account is enabled. <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="sys-ps-is-account-enabled-parameters"> </a> Parameters </h5> </div> </div> </div> <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> in_host VARCHAR(60) </code> : The host name of the account to check. </li> <li class="listitem"> <code class="literal"> in_user VARCHAR(32) </code> : The user name of the account to check. </li> </ul> </div> </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="sys-ps-is-account-enabled-return-value"> </a> Return Value </h5> </div> </div> </div> An <code class="literal"> ENUM('YES','NO') </code> value. </div> <div class="simplesect"> <div class="titlepage"> <div> <div class="simple"> <h5 class="title"> <a name="sys-ps-is-account-enabled-example"> </a> Example </h5> </div> </div> </div> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa92271033"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT sys.ps_is_account_enabled('localhost', 'root'); +------------------------------------------------+ | sys.ps_is_account_enabled('localhost', 'root') | +------------------------------------------------+ | YES | +------------------------------------------------+</code></pre> </div> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/source-installation.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h2 class="title"> <a name="source-installation"> </a> 2.8 Installing MySQL from Source </h2> </div> </div> </div> <div class="toc"> <dl class="toc"> <dt> <a href="source-installation-methods.html"> 2.8.1 Source Installation Methods </a> </dt> <dt> <a href="source-installation-prerequisites.html"> 2.8.2 Source Installation Prerequisites </a> </dt> <dt> <a href="source-installation-layout.html"> 2.8.3 MySQL Layout for Source Installation </a> </dt> <dt> <a href="installing-source-distribution.html"> 2.8.4 Installing MySQL Using a Standard Source Distribution </a> </dt> <dt> <a href="installing-development-tree.html"> 2.8.5 Installing MySQL Using a Development Source Tree </a> </dt> <dt> <a href="source-ssl-library-configuration.html"> 2.8.6 Configuring SSL Library Support </a> </dt> <dt> <a href="source-configuration-options.html"> 2.8.7 MySQL Source-Configuration Options </a> </dt> <dt> <a href="compilation-problems.html"> 2.8.8 Dealing with Problems Compiling MySQL </a> </dt> <dt> <a href="source-configuration-third-party.html"> 2.8.9 MySQL Configuration and Third-Party Tools </a> </dt> <dt> <a href="source-installation-doxygen.html"> 2.8.10 Generating MySQL Doxygen Documentation Content </a> </dt> </dl> </div> <a class="indexterm" name="idm46045329722592"> </a> <a class="indexterm" name="idm46045329721136"> </a> <a class="indexterm" name="idm46045329719648"> </a> Building MySQL from the source code enables you to customize build parameters, compiler optimizations, and installation location. For a list of systems on which MySQL is known to run, see <a class="ulink" href="https://www.mysql.com/support/supportedplatforms/database.html" target="_blank"> https://www.mysql.com/support/supportedplatforms/database.html </a> . Before you proceed with an installation from source, check whether Oracle produces a precompiled binary distribution for your platform and whether it works for you. We put a great deal of effort into ensuring that our binaries are built with the best possible options for optimal performance. Instructions for installing binary distributions are available in <a class="xref" href="binary-installation.html" title="2.2 Installing MySQL on Unix/Linux Using Generic Binaries"> Section 2.2, “Installing MySQL on Unix/Linux Using Generic Binaries” </a> . <a class="indexterm" name="idm46045329715904"> </a> If you are interested in building MySQL from a source distribution using build options the same as or similar to those use by Oracle to produce binary distributions on your platform, obtain a binary distribution, unpack it, and look in the <code class="filename"> docs/INFO_BIN </code> file, which contains information about how that MySQL distribution was configured and compiled. <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;"> <div class="admon-title"> Warning </div> Building MySQL with nonstandard options may lead to reduced functionality, performance, or security. </div> The MySQL source code contains internal documentation written using Doxygen. The generated Doxygen content is available at <a class="ulink" href="/doc/index-other.html" target="_top"> https://dev.mysql.com/doc/index-other.html </a> . It is also possible to generate this content locally from a MySQL source distribution using the instructions at <a class="xref" href="source-installation-doxygen.html" title="2.8.10 Generating MySQL Doxygen Documentation Content"> Section 2.8.10, “Generating MySQL Doxygen Documentation Content” </a> . </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-processes.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h4 class="title"> <a name="mysql-cluster-ndbinfo-processes"> </a> 25.6.17.51 The ndbinfo processes Table </h4> </div> </div> </div> <a class="indexterm" name="idm46045088252656"> </a> This table contains information about NDB Cluster node processes; each node is represented by the row in the table. Only nodes that are connected to the cluster are shown in this table. You can obtain information about nodes that are configured but not connected to the cluster from the <a class="link" href="mysql-cluster-ndbinfo-nodes.html" title="25.6.17.48 The ndbinfo nodes Table"> <code class="literal"> nodes </code> </a> and <a class="link" href="mysql-cluster-ndbinfo-config-nodes.html" title="25.6.17.10 The ndbinfo config_nodes Table"> <code class="literal"> config_nodes </code> </a> tables. The <code class="literal"> processes </code> table contains the following columns: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> node_id </code> The node's unique node ID in the cluster </li> <li class="listitem"> <code class="literal"> node_type </code> Type of node (management, data, or API node; see text) </li> <li class="listitem"> <code class="literal"> node_version </code> Version of the <code class="literal"> NDB </code> software program running on this node. </li> <li class="listitem"> <code class="literal"> process_id </code> This node's process ID </li> <li class="listitem"> <code class="literal"> angel_process_id </code> Process ID of this node's angel process </li> <li class="listitem"> <code class="literal"> process_name </code> Name of the executable </li> <li class="listitem"> <code class="literal"> service_URI </code> Service URI of this node (see text) </li> </ul> </div> <h5> <a name="idm46045088232096"> </a> Notes </h5> <code class="literal"> node_id </code> is the ID assigned to this node in the cluster. The <code class="literal"> node_type </code> column displays one of the following three values: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <code class="literal"> MGM </code> : Management node. </li> <li class="listitem"> <code class="literal"> NDB </code> : Data node. </li> <li class="listitem"> <code class="literal"> API </code> : API or SQL node. </li> </ul> </div> For an executable shipped with the NDB Cluster distribution, <code class="literal"> node_version </code> shows the software Cluster version string, such as <code class="literal"> 8.4.0-ndb-8.4.0 </code> . <code class="literal"> process_id </code> is the node executable's process ID as shown by the host operating system using a process display application such as top on Linux, or the Task Manager on Windows platforms. <code class="literal"> angel_process_id </code> is the system process ID for the node's angel process, which ensures that a data node or SQL is automatically restarted in cases of failures. For management nodes and API nodes other than SQL nodes, the value of this column is <code class="literal"> NULL </code> . The <code class="literal"> process_name </code> column shows the name of the running executable. For management nodes, this is <code class="literal"> ndb_mgmd </code> . For data nodes, this is <code class="literal"> ndbd </code> (single-threaded) or <code class="literal"> ndbmtd </code> (multithreaded). For SQL nodes, this is <code class="literal"> mysqld </code> . For other types of API nodes, it is the name of the executable program connected to the cluster; NDB API applications can set a custom value for this using <a class="ulink" href="/doc/ndbapi/en/ndb-ndb-cluster-connection.html#ndb-ndb-cluster-connection-set-name" target="_top"> <code class="literal"> Ndb_cluster_connection::set_name() </code> </a> . <code class="literal"> service_URI </code> shows the service network address. For management nodes and data nodes, the scheme used is <code class="literal"> ndb:// </code> . For SQL nodes, this is <code class="literal"> mysql:// </code> . By default, API nodes other than SQL nodes use <code class="literal"> ndb:// </code> for the scheme; NDB API applications can set this to a custom value using <code class="literal"> Ndb_cluster_connection::set_service_uri() </code> . regardless of the node type, the scheme is followed by the IP address used by the NDB transporter for the node in question. For management nodes and SQL nodes, this address includes the port number (usually 1186 for management nodes and 3306 for SQL nodes). If the SQL node was started with the <a class="link" href="server-system-variables.html#sysvar_bind_address"> <code class="literal"> bind_address </code> </a> system variable set, this address is used instead of the transporter address, unless the bind address is set to <code class="literal"> * </code> , <code class="literal"> 0.0.0.0 </code> , or <code class="literal"> :: </code> . Additional path information may be included in the <code class="literal"> service_URI </code> value for an SQL node reflecting various configuration options. For example, <code class="literal"> mysql://198.51.100.3/tmp/mysql.sock </code> indicates that the SQL node was started with the <a class="link" href="server-system-variables.html#sysvar_skip_networking"> <code class="literal"> skip_networking </code> </a> system variable enabled, and <code class="literal"> mysql://198.51.100.3:3306/?server-id=1 </code> shows that replication is enabled for this SQL node. </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/json-utility-functions.html

<div id="docs-body"> <div class="section"> <div class="titlepage"> <div> <div> <h3 class="title"> <a name="json-utility-functions"> </a> 14.17.8 JSON Utility Functions </h3> </div> </div> </div> This section documents utility functions that act on JSON values, or strings that can be parsed as JSON values. <a class="link" href="json-utility-functions.html#function_json-pretty"> <code class="literal"> JSON_PRETTY() </code> </a> prints out a JSON value in a format that is easy to read. <a class="link" href="json-utility-functions.html#function_json-storage-size"> <code class="literal"> JSON_STORAGE_SIZE() </code> </a> and <a class="link" href="json-utility-functions.html#function_json-storage-free"> <code class="literal"> JSON_STORAGE_FREE() </code> </a> show, respectively, the amount of storage space used by a given JSON value and the amount of space remaining in a <code class="literal"> JSON </code> column following a partial update. <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <a name="function_json-pretty"> </a> <a class="link" href="json-utility-functions.html#function_json-pretty"> <code class="literal"> JSON_PRETTY( <code> json_val </code> ) </code> </a> <a class="indexterm" name="idm46045194253936"> </a> Provides pretty-printing of JSON values similar to that implemented in PHP and by other languages and database systems. The value supplied must be a JSON value or a valid string representation of a JSON value. Extraneous whitespaces and newlines present in this value have no effect on the output. For a <code class="literal"> NULL </code> value, the function returns <code class="literal"> NULL </code> . If the value is not a JSON document, or if it cannot be parsed as one, the function fails with an error. Formatting of the output from this function adheres to the following rules: <div class="itemizedlist"> <ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> Each array element or object member appears on a separate line, indented by one additional level as compared to its parent. </li> <li class="listitem"> Each level of indentation adds two leading spaces. </li> <li class="listitem"> A comma separating individual array elements or object members is printed before the newline that separates the two elements or members. </li> <li class="listitem"> The key and the value of an object member are separated by a colon followed by a space (' <code class="literal"> : </code> '). </li> <li class="listitem"> An empty object or array is printed on a single line. No space is printed between the opening and closing brace. </li> <li class="listitem"> Special characters in string scalars and key names are escaped employing the same rules used by the <a class="link" href="json-creation-functions.html#function_json-quote"> <code class="literal"> JSON_QUOTE() </code> </a> function. </li> </ul> </div> <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa27010127"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT JSON_PRETTY('123'); # scalar +--------------------+ | JSON_PRETTY('123') | +--------------------+ | 123 | +--------------------+ mysql> SELECT JSON_PRETTY("[1,3,5]"); # array +------------------------+ | JSON_PRETTY("[1,3,5]") | +------------------------+ | [ 1, 3, 5 ] | +------------------------+ mysql> SELECT JSON_PRETTY('{"a":"10","b":"15","x":"25"}'); # object +---------------------------------------------+ | JSON_PRETTY('{"a":"10","b":"15","x":"25"}') | +---------------------------------------------+ | { "a": "10", "b": "15", "x": "25" } | +---------------------------------------------+ mysql> SELECT JSON_PRETTY('["a",1,{"key1": '> "value1"},"5", "77" , '> {"key2":["value3","valueX", '> "valueY"]},"j", "2" ]')\G # nested arrays and objects *************************** 1. row *************************** JSON_PRETTY('["a",1,{"key1": "value1"},"5", "77" , {"key2":["value3","valuex", "valuey"]},"j", "2" ]'): [ "a", 1, { "key1": "value1" }, "5", "77", { "key2": [ "value3", "valuex", "valuey" ] }, "j", "2" ]</code></pre> </div> </li> <li class="listitem"> <a name="function_json-storage-free"> </a> <a class="link" href="json-utility-functions.html#function_json-storage-free"> <code class="literal"> JSON_STORAGE_FREE( <code> json_val </code> ) </code> </a> <a class="indexterm" name="idm46045194228128"> </a> For a <a class="link" href="json.html" title="13.5 The JSON Data Type"> <code class="literal"> JSON </code> </a> column value, this function shows how much storage space was freed in its binary representation after it was updated in place using <a class="link" href="json-modification-functions.html#function_json-set"> <code class="literal"> JSON_SET() </code> </a> , <a class="link" href="json-modification-functions.html#function_json-replace"> <code class="literal"> JSON_REPLACE() </code> </a> , or <a class="link" href="json-modification-functions.html#function_json-remove"> <code class="literal"> JSON_REMOVE() </code> </a> . The argument can also be a valid JSON document or a string which can be parsed as one—either as a literal value or as the value of a user variable—in which case the function returns 0. It returns a positive, nonzero value if the argument is a <code class="literal"> JSON </code> column value which has been updated as described previously, such that its binary representation takes up less space than it did prior to the update. For a <code class="literal"> JSON </code> column which has been updated such that its binary representation is the same as or larger than before, or if the update was not able to take advantage of a partial update, it returns 0; it returns <code class="literal"> NULL </code> if the argument is <code class="literal"> NULL </code> . If <code> json_val </code> is not <code class="literal"> NULL </code> , and neither is a valid JSON document nor can be successfully parsed as one, an error results. In this example, we create a table containing a <code class="literal"> JSON </code> column, then insert a row containing a JSON object: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa52974016"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> CREATE TABLE jtable (jcol JSON); Query OK, 0 rows affected (0.38 sec) mysql> INSERT INTO jtable VALUES -> ('{"a": 10, "b": "wxyz", "c": "[true, false]"}'); Query OK, 1 row affected (0.04 sec) mysql> SELECT * FROM jtable; +----------------------------------------------+ | jcol | +----------------------------------------------+ | {"a": 10, "b": "wxyz", "c": "[true, false]"} | +----------------------------------------------+ 1 row in set (0.00 sec)</code></pre> </div> Now we update the column value using <code class="literal"> JSON_SET() </code> such that a partial update can be performed; in this case, we replace the value pointed to by the <code class="literal"> c </code> key (the array <code class="literal"> [true, false] </code> ) with one that takes up less space (the integer <code class="literal"> 1 </code> ): <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa80443634"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> UPDATE jtable -> SET jcol = JSON_SET(jcol, "$.a", 10, "$.b", "wxyz", "$.c", 1); Query OK, 1 row affected (0.03 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> SELECT * FROM jtable; +--------------------------------+ | jcol | +--------------------------------+ | {"a": 10, "b": "wxyz", "c": 1} | +--------------------------------+ 1 row in set (0.00 sec) mysql> SELECT JSON_STORAGE_FREE(jcol) FROM jtable; +-------------------------+ | JSON_STORAGE_FREE(jcol) | +-------------------------+ | 14 | +-------------------------+ 1 row in set (0.00 sec)</code></pre> </div> The effects of successive partial updates on this free space are cumulative, as shown in this example using <code class="literal"> JSON_SET() </code> to reduce the space taken up by the value having key <code class="literal"> b </code> (and making no other changes): <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa4410044"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> UPDATE jtable -> SET jcol = JSON_SET(jcol, "$.a", 10, "$.b", "wx", "$.c", 1); Query OK, 1 row affected (0.03 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> SELECT JSON_STORAGE_FREE(jcol) FROM jtable; +-------------------------+ | JSON_STORAGE_FREE(jcol) | +-------------------------+ | 16 | +-------------------------+ 1 row in set (0.00 sec)</code></pre> </div> Updating the column without using <code class="literal"> JSON_SET() </code> , <code class="literal"> JSON_REPLACE() </code> , or <code class="literal"> JSON_REMOVE() </code> means that the optimizer cannot perform the update in place; in this case, <code class="literal"> JSON_STORAGE_FREE() </code> returns 0, as shown here: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa95017245"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> UPDATE jtable SET jcol = '{"a": 10, "b": 1}'; Query OK, 1 row affected (0.05 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> SELECT JSON_STORAGE_FREE(jcol) FROM jtable; +-------------------------+ | JSON_STORAGE_FREE(jcol) | +-------------------------+ | 0 | +-------------------------+ 1 row in set (0.00 sec)</code></pre> </div> Partial updates of JSON documents can be performed only on column values. For a user variable that stores a JSON value, the value is always completely replaced, even when the update is performed using <code class="literal"> JSON_SET() </code> : <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa93070926"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SET @j = '{"a": 10, "b": "wxyz", "c": "[true, false]"}'; Query OK, 0 rows affected (0.00 sec) mysql> SET @j = JSON_SET(@j, '$.a', 10, '$.b', 'wxyz', '$.c', '1'); Query OK, 0 rows affected (0.00 sec) mysql> SELECT @j, JSON_STORAGE_FREE(@j) AS Free; +----------------------------------+------+ | @j | Free | +----------------------------------+------+ | {"a": 10, "b": "wxyz", "c": "1"} | 0 | +----------------------------------+------+ 1 row in set (0.00 sec)</code></pre> </div> For a JSON literal, this function always returns 0: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa94593370"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT JSON_STORAGE_FREE('{"a": 10, "b": "wxyz", "c": "1"}') AS Free; +------+ | Free | +------+ | 0 | +------+ 1 row in set (0.00 sec)</code></pre> </div> </li> <li class="listitem"> <a name="function_json-storage-size"> </a> <a class="link" href="json-utility-functions.html#function_json-storage-size"> <code class="literal"> JSON_STORAGE_SIZE( <code> json_val </code> ) </code> </a> <a class="indexterm" name="idm46045194177200"> </a> This function returns the number of bytes used to store the binary representation of a JSON document. When the argument is a <code class="literal"> JSON </code> column, this is the space used to store the JSON document as it was inserted into the column, prior to any partial updates that may have been performed on it afterwards. <code> json_val </code> must be a valid JSON document or a string which can be parsed as one. In the case where it is string, the function returns the amount of storage space in the JSON binary representation that is created by parsing the string as JSON and converting it to binary. It returns <code class="literal"> NULL </code> if the argument is <code class="literal"> NULL </code> . An error results when <code> json_val </code> is not <code class="literal"> NULL </code> , and is not—or cannot be successfully parsed as—a JSON document. To illustrate this function's behavior when used with a <code class="literal"> JSON </code> column as its argument, we create a table named <code class="literal"> jtable </code> containing a <code class="literal"> JSON </code> column <code class="literal"> jcol </code> , insert a JSON value into the table, then obtain the storage space used by this column with <code class="literal"> JSON_STORAGE_SIZE() </code> , as shown here: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa24605229"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> CREATE TABLE jtable (jcol JSON); Query OK, 0 rows affected (0.42 sec) mysql> INSERT INTO jtable VALUES -> ('{"a": 1000, "b": "wxyz", "c": "[1, 3, 5, 7]"}'); Query OK, 1 row affected (0.04 sec) mysql> SELECT -> jcol, -> JSON_STORAGE_SIZE(jcol) AS Size, -> JSON_STORAGE_FREE(jcol) AS Free -> FROM jtable; +-----------------------------------------------+------+------+ | jcol | Size | Free | +-----------------------------------------------+------+------+ | {"a": 1000, "b": "wxyz", "c": "[1, 3, 5, 7]"} | 47 | 0 | +-----------------------------------------------+------+------+ 1 row in set (0.00 sec)</code></pre> </div> According to the output of <code class="literal"> JSON_STORAGE_SIZE() </code> , the JSON document inserted into the column takes up 47 bytes. We also checked the amount of space freed by any previous partial updates of the column using <a class="link" href="json-utility-functions.html#function_json-storage-free"> <code class="literal"> JSON_STORAGE_FREE() </code> </a> ; since no updates have yet been performed, this is 0, as expected. Next we perform an <a class="link" href="update.html" title="15.2.17 UPDATE Statement"> <code class="literal"> UPDATE </code> </a> on the table that should result in a partial update of the document stored in <code class="literal"> jcol </code> , and then test the result as shown here: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa22006261"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> UPDATE jtable SET jcol = -> JSON_SET(jcol, "$.b", "a"); Query OK, 1 row affected (0.04 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> SELECT -> jcol, -> JSON_STORAGE_SIZE(jcol) AS Size, -> JSON_STORAGE_FREE(jcol) AS Free -> FROM jtable; +--------------------------------------------+------+------+ | jcol | Size | Free | +--------------------------------------------+------+------+ | {"a": 1000, "b": "a", "c": "[1, 3, 5, 7]"} | 47 | 3 | +--------------------------------------------+------+------+ 1 row in set (0.00 sec)</code></pre> </div> The value returned by <code class="literal"> JSON_STORAGE_FREE() </code> in the previous query indicates that a partial update of the JSON document was performed, and that this freed 3 bytes of space used to store it. The result returned by <code class="literal"> JSON_STORAGE_SIZE() </code> is unchanged by the partial update. Partial updates are supported for updates using <a class="link" href="json-modification-functions.html#function_json-set"> <code class="literal"> JSON_SET() </code> </a> , <a class="link" href="json-modification-functions.html#function_json-replace"> <code class="literal"> JSON_REPLACE() </code> </a> , or <a class="link" href="json-modification-functions.html#function_json-remove"> <code class="literal"> JSON_REMOVE() </code> </a> . The direct assignment of a value to a <code class="literal"> JSON </code> column cannot be partially updated; following such an update, <code class="literal"> JSON_STORAGE_SIZE() </code> always shows the storage used for the newly-set value: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa1693583"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> UPDATE jtable mysql> SET jcol = '{"a": 4.55, "b": "wxyz", "c": "[true, false]"}'; Query OK, 1 row affected (0.04 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> SELECT -> jcol, -> JSON_STORAGE_SIZE(jcol) AS Size, -> JSON_STORAGE_FREE(jcol) AS Free -> FROM jtable; +------------------------------------------------+------+------+ | jcol | Size | Free | +------------------------------------------------+------+------+ | {"a": 4.55, "b": "wxyz", "c": "[true, false]"} | 56 | 0 | +------------------------------------------------+------+------+ 1 row in set (0.00 sec)</code></pre> </div> A JSON user variable cannot be partially updated. This means that this function always shows the space currently used to store a JSON document in a user variable: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa72757799"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SET @j = '[100, "sakila", [1, 3, 5], 425.05]'; Query OK, 0 rows affected (0.00 sec) mysql> SELECT @j, JSON_STORAGE_SIZE(@j) AS Size; +------------------------------------+------+ | @j | Size | +------------------------------------+------+ | [100, "sakila", [1, 3, 5], 425.05] | 45 | +------------------------------------+------+ 1 row in set (0.00 sec) mysql> SET @j = JSON_SET(@j, '$[1]', "json"); Query OK, 0 rows affected (0.00 sec) mysql> SELECT @j, JSON_STORAGE_SIZE(@j) AS Size; +----------------------------------+------+ | @j | Size | +----------------------------------+------+ | [100, "json", [1, 3, 5], 425.05] | 43 | +----------------------------------+------+ 1 row in set (0.00 sec) mysql> SET @j = JSON_SET(@j, '$[2][0]', JSON_ARRAY(10, 20, 30)); Query OK, 0 rows affected (0.00 sec) mysql> SELECT @j, JSON_STORAGE_SIZE(@j) AS Size; +---------------------------------------------+------+ | @j | Size | +---------------------------------------------+------+ | [100, "json", [[10, 20, 30], 3, 5], 425.05] | 56 | +---------------------------------------------+------+ 1 row in set (0.00 sec)</code></pre> </div> For a JSON literal, this function always returns the current storage space used: <div class="copytoclipboard-wrapper"> <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99951128"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"></button></div></div><code class="language-sql">mysql> SELECT -> JSON_STORAGE_SIZE('[100, "sakila", [1, 3, 5], 425.05]') AS A, -> JSON_STORAGE_SIZE('{"a": 1000, "b": "a", "c": "[1, 3, 5, 7]"}') AS B, -> JSON_STORAGE_SIZE('{"a": 1000, "b": "wxyz", "c": "[1, 3, 5, 7]"}') AS C, -> JSON_STORAGE_SIZE('[100, "json", [[10, 20, 30], 3, 5], 425.05]') AS D; +----+----+----+----+ | A | B | C | D | +----+----+----+----+ | 45 | 44 | 47 | 56 | +----+----+----+----+ 1 row in set (0.00 sec)</code></pre> </div> </li> </ul> </div> </div> </div>

https://dev.mysql.com/doc/refman/8.4/en/innodb-information-schema-metrics-table.html