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https://dev.mysql.com/doc/refman/8.4/en/outer-join-simplification.html
Table expressions in the FROM clause of a query are simplified in many cases. When the optimizer evaluates plans for outer join operations, it takes into consideration only plans where, for each such operation, the outer tables are accessed before ...At the parser stage, queries with right outer join operations are converted to equivalent queries containing only left join ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-atom-molecule-events.html
For a table I/O event, there are usually two rows in events_waits_current, not one. For example, a row fetch might result in rows like this: Row# EVENT_NAME TIMER_START TIMER_END ---- ---------- ----------- --------- 1 wait/io/file/myisam/dfile ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-query-profiling.html
The setup_actors table can be used to limit the collection of historical events by host, user, or account to reduce runtime overhead and the amount of data collected in history tables. For example: mysql> SELECT * FROM employees.employees WHERE ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-runtime-configuration.html
If you have the UPDATE privilege, you can change Performance Schema operation by modifying setup tables to affect how monitoring occurs. For additional details about these tables, see Section 29.12.2, “Performance Schema Setup Tables”. The ...
https://dev.mysql.com/doc/refman/8.4/en/replication-multi-source-monitoring.html
To monitor the status of replication channels the following options exist: Using the replication Performance Schema tables. The information that was available through these variables has been migrated to the replication performance tables. This ...
https://dev.mysql.com/doc/refman/8.4/en/sys-schema-progress-reporting.html
The following sys schema views provide progress reporting for long-running transactions: processlist session x$processlist x$session Assuming that the required instruments and consumers are enabled, the progress column of these views shows the ...
https://dev.mysql.com/doc/refman/8.4/en/using-explain.html
That is, MySQL explains how it would process the statement, including information about how tables are joined and in which order. With the help of EXPLAIN, you can see where you should add indexes to tables so that the statement executes faster by ... The EXPLAIN statement provides information about how MySQL executes statements: EXPLAIN works with SELECT, DELETE, INSERT, REPLACE, and UPDATE ...
https://dev.mysql.com/doc/refman/8.4/en/using-log-files.html
Note that before starting mysqld with the general query log enabled, you should check all your tables with myisamchk. If this happens, you should check all your tables with myisamchk (see Chapter 7, MySQL Server Administration), and test the ...If ...
https://dev.mysql.com/doc/mysql-shell/9.4/en/mysql-shell-autocompletion.html
Autocompletion supports the following text objects: In SQL mode, autocompletion is aware of schema names, table names, column names of the current active schema. SELECT schema1.table1.column1 FR: the prefix is 'FR', no qualifier is present. For ...
https://dev.mysql.com/doc/mysql-ai/9.4/en/mys-mysqlai-ml-metrics.html
If the input table overlaps with the training table, and remove_seen is true, which is the default setting, then the model will not repeat a recommendation and it ignores the overlap items. The precision_at_k value for the input table is the average ... The ML_TRAIN routine includes the optimization_metric option, and the ML_SCORE routine includes the metric ...