MySQL 9.3 Reference Manual Including MySQL NDB Cluster 9.3
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.