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https://dev.mysql.com/doc/refman/8.0/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/8.0/en/performance-schema-clone-progress-table.html
Note The Performance Schema table described here is available as of MySQL 8.0.17. The clone_progress table shows progress information for the current or last executed cloning operation only. The stages of a cloning operation include DROP DATA, FILE ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-events-stages-current-table.html
The table stores one row per thread showing the current status of the thread's most recent monitored stage event, so there is no system variable for configuring the table size. Of the tables that contain stage event rows, events_stages_current is ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-mutex-instances-table.html
The mutex_instances table lists all the mutexes seen by the Performance Schema while the server executes. A mutex is a synchronization mechanism used in the code to enforce that only one thread at a given time can have access to some common ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-obtaining-parent-events.html
Rows of this table have a THREAD_ID column indicating the thread ID of the session that owns the lock, and an EVENT_ID column indicating the Performance Schema event that caused the lock. The relation is based on a nested set data model, so the join ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-stage-tables.html
The Performance Schema instruments stages, which are steps during the statement-execution process, such as parsing a statement, opening a table, or performing a filesort operation. Stages correspond to the thread states displayed by SHOW ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-table-wait-summary-tables.html
The following sections describe the table I/O and lock wait summary tables: table_io_waits_summary_by_index_usage: Table I/O waits per index table_io_waits_summary_by_table: Table I/O waits per table table_lock_waits_summary_by_table: Table lock ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-user-defined-functions-table.html
The user_defined_functions table contains a row for each loadable function registered automatically by a component or plugin, or manually by a CREATE FUNCTION statement. For information about operations that add or remove table rows, see Section ...
https://dev.mysql.com/doc/refman/8.0/en/prepare.html
PREPARE stmt_name FROM preparable_stmt The PREPARE statement prepares a SQL statement and assigns it a name, stmt_name, by which to refer to the statement later. The prepared statement is executed with EXECUTE and released with DEALLOCATE PREPARE.
https://dev.mysql.com/doc/refman/8.0/en/primary-key-optimization.html
The primary key for a table represents the column or set of columns that you use in your most vital queries. Query performance benefits from the NOT NULL optimization, because it cannot include any NULL values. With the InnoDB storage engine, the ...