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https://dev.mysql.com/doc/refman/8.0/en/performance-schema-prepared-statements-instances-table.html
The Performance Schema provides instrumentation for prepared statements, for which there are two protocols: The binary protocol. This is accessed through the MySQL C API and maps onto underlying server commands as shown in the following table. C ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-rwlock-instances-table.html
The rwlock_instances table lists all the rwlock (read write lock) instances seen by the Performance Schema while the server executes. An rwlock is a synchronization mechanism used in the code to enforce that threads at a given time can have access ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-system-variables.html
This implementation queries active thread data from the Performance Schema rather than the thread manager and does not require a mutex. The Performance Schema automatically sizes the values of several of its parameters at server startup if they are ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-tp-thread-group-state-table.html
That is, these two queries are equivalent: SELECT TP_GROUP_ID, MAX_THREAD_IDS_IN_GROUP FROM tp_thread_group_state; SELECT TP_GROUP_ID, MAX(TP_THREAD_NUMBER) FROM tp_thread_state GROUP BY TP_GROUP_ID; The tp_thread_group_state table has these ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-variables-info-table.html
The variables_info table shows, for each system variable, the source from which it was most recently set, and its range of values. VARIABLE_SOURCE The source from which the variable was most recently set: COMMAND_LINE The variable was set on the ...
https://dev.mysql.com/doc/refman/8.0/en/persisted-system-variables.html
The MySQL server maintains system variables that configure its operation. A system variable can have a global value that affects server operation as a whole, a session value that affects the current session, or both. Many system variables are ...
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/preventing-use-of-optimizer-trace.html
If, for some reason, you wish to prevent users from seeing traces of their queries, start the server with the options shown here: --maximum-optimizer-trace-max-mem-size=0 --optimizer-trace-max-mem-size=0 This sets the maximum size to 0 and prevents ...
https://dev.mysql.com/doc/refman/8.0/en/problems-with-float.html
Floating-point numbers sometimes cause confusion because they are approximate and not stored as exact values. A floating-point value as written in an SQL statement may not be the same as the value represented internally. Attempts to treat ...
https://dev.mysql.com/doc/refman/8.0/en/processlist-access.html
The following discussion enumerates the sources of process information, the privileges required to see process information, and describes the content of process list entries. The other sources have negative performance consequences because they ...