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https://dev.mysql.com/doc/refman/8.0/en/performance-schema-performance-timers-table.html
The Performance Schema determines this value by invoking the timer 20 times during initialization and picking the smallest value. The total overhead really is twice this amount because the instrumentation invokes the timer at the start and end of ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-ndbinfo-threadstat.html
The values of the os_ru_utime, os_ru_stime, os_ru_minflt, os_ru_majflt, os_ru_nvcsw, and os_ru_nivcsw columns are obtained using the system getrusage() call, or the equivalent. Since this table contains counts taken at a given point in time, for ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-status-variables.html
Performance Schema status variables have the following meanings: Performance_schema_accounts_lost The number of times a row could not be added to the accounts table because it was full. Performance_schema_hosts_lost The number of times a row could ...Performance_schema_digest_lost The number of digest instances that could not be instrumented in the events_statements_summary_by_digest ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-tp-thread-group-stats-table.html
WAKE_THREAD_STALL_CHECKER The number of times the stall check thread decided to wake or create a thread to possibly handle some statements or take care of the waiter thread role. PRIO_KICKUPS The number of statements that have been moved from ...
https://dev.mysql.com/doc/refman/8.0/en/thread-pool-information-schema-tables.html
They provide information about thread pool operation: TP_THREAD_GROUP_STATE: Information about thread pool thread group states TP_THREAD_GROUP_STATS: Thread group statistics TP_THREAD_STATE: Information about thread pool thread states Rows in these ... Note As of MySQL 8.0.14, the INFORMATION_SCHEMA thread pool tables are also available as Performance Schema ...
https://dev.mysql.com/doc/refman/8.0/en/dynamic-format.html
A row can become fragmented (stored in noncontiguous pieces) when it is made longer as a result of an update. If a string column has a length of zero after trailing space removal, or a numeric column has a value of zero, it is marked in the bitmap ... Dynamic storage format is used if a MyISAM table contains any variable-length columns (VARCHAR, VARBINARY, BLOB, or TEXT), or if the table was created with the ROW_FORMAT=DYNAMIC table ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-table-handles-table.html
The Performance Schema exposes table lock information through the table_handles table to show the table locks currently in effect for each opened table handle. This information shows which table handles the server has open, how they are locked, and ...The value is one of READ, READ WITH SHARED LOCKS, READ HIGH PRIORITY, READ NO INSERT, WRITE ALLOW WRITE, WRITE CONCURRENT INSERT, WRITE LOW PRIORITY, or ...
https://dev.mysql.com/doc/refman/8.0/en/program-variables.html
Many MySQL programs have internal variables that can be set at runtime using the SET statement. See Section 15.7.6.1, “SET Syntax for Variable Assignment”, and Section 7.1.9, “Using System Variables”. To set the max_allowed_packet variable ...Most of these program variables also can be set at server startup by using the same syntax that applies to specifying program ...
https://dev.mysql.com/doc/refman/8.0/en/using-gdb-on-mysqld.html
In this case, you can only have one thread active at a time. Use the --gdb option to mysqld to install an interrupt handler for SIGINT (needed to stop mysqld with ^C to set breakpoints) and disable stack tracing and core file handling. It is very ...
https://dev.mysql.com/doc/refman/8.0/en/aggregate-functions-and-modifiers.html
They are often used with a GROUP BY clause to group values into subsets. For information about aggregate functions that operate on geometry values, see Section 14.16.12, “Spatial Aggregate Functions”.