29.12 Performance Schema Table Descriptions

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MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4

Tables in the performance_schema database can be grouped as follows:

• Setup tables. These tables are used to configure and display monitoring characteristics.
• Current events tables. The events_waits_current table contains the most recent event for each thread. Other similar tables contain current events at different levels of the event hierarchy: events_stages_current for stage events, events_statements_current for statement events, and events_transactions_current for transaction events.
• History tables. These tables have the same structure as the current events tables, but contain more rows. For example, for wait events, events_waits_history table contains the most recent 10 events per thread. events_waits_history_long contains the most recent 10,000 events. Other similar tables exist for stage, statement, and transaction histories.

To change the sizes of the history tables, set the appropriate system variables at server startup. For example, to set the sizes of the wait event history tables, set performance_schema_events_waits_history_size and performance_schema_events_waits_history_long_size. - Summary tables. These tables contain information aggregated over groups of events, including those that have been discarded from the history tables. - Instance tables. These tables document what types of objects are instrumented. An instrumented object, when used by the server, produces an event. These tables provide event names and explanatory notes or status information. - Miscellaneous tables. These do not fall into any of the other table groups.