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https://dev.mysql.com/doc/refman/8.4/en/innodb-standard-monitor.html
Contention can be due to heavy parallelism of queries or problems in operating system thread scheduling. You can calculate from these numbers how many data file I/O operations your queries currently are doing. The Lock Monitor is the same as the ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-undo-tablespaces.html
Undo tablespaces contain undo logs, which are collections of records containing information about how to undo the latest change by a transaction to a clustered index record. Default undo tablespaces are created at initialization time to provide a ...
https://dev.mysql.com/doc/refman/8.4/en/partitioning-limitations.html
As with nonpartitioned tables, proper use of indexes can speed up queries on partitioned tables significantly. In addition, designing partitioned tables and queries on these tables to take advantage of partition pruning can improve performance ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-events-waits-current-table.html
The table stores one row per thread showing the current status of the thread's most recent monitored wait event, so there is no system variable for configuring the table size. Of the tables that contain wait event rows, events_waits_current is the ...
https://dev.mysql.com/doc/refman/8.4/en/server-options.html
When you start the mysqld server, you can specify program options using any of the methods described in Section 6.2.2, “Specifying Program Options”. The most common methods are to provide options in an option file or on the command line.
https://dev.mysql.com/doc/refman/8.4/en/show-warnings.html
SHOW WARNINGS [LIMIT [offset,] row_count] SHOW COUNT(*) WARNINGS SHOW WARNINGS is a diagnostic statement that displays information about the conditions (errors, warnings, and notes) resulting from executing a statement in the current session.
https://dev.mysql.com/doc/refman/8.4/en/subquery-optimization-with-exists.html
WHERE subquery_where) MySQL evaluates queries “from outside to inside.” That is, it first obtains the value of the outer expression outer_expr, and then runs the subquery and captures the rows that it produces. This is a problem because many ...
https://dev.mysql.com/doc/refman/8.4/en/window-function-optimization.html
Semijoins are not applicable to window function optimization because semijoins apply to subqueries in WHERE and JOIN ... Window functions affect the strategies the optimizer considers: Derived table merging for a subquery is disabled if the ...
https://dev.mysql.com/doc/refman/8.4/en/window-functions-named-windows.html
Windows can be defined and given names by which to refer to them in OVER clauses. If present in a query, the WINDOW clause falls between the positions of the HAVING and ORDER BY clauses, and has this syntax: WINDOW window_name AS (window_spec) [, ...
https://dev.mysql.com/doc/relnotes/connector-j/en/news-8-0-13.html
It was due to the intermediate queries for enabling multiquery support on the server resetting the local transaction state as a side effect. With this fix, the local transaction state is preserved when the intermediate queries are executed. (Bug ...