MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0

26.4.3 Event Pre-Filtering

Pre-filtering is done by the Performance Schema and has a global effect that applies to all users. Pre-filtering can be applied to either the producer or consumer stage of event processing:

Modifications to any of these tables affect monitoring immediately, with the exception that modifications to the setup_actors table affect only foreground threads created subsequent to the modification, not existing threads.

When you change the monitoring configuration, the Performance Schema does not flush the history tables. Events already collected remain in the current-events and history tables until displaced by newer events. If you disable instruments, you might need to wait a while before events for them are displaced by newer events of interest. Alternatively, use TRUNCATE TABLE to empty the history tables.

After making instrumentation changes, you might want to truncate the summary tables. Generally, the effect is to reset the summary columns to 0 or NULL, not to remove rows. This enables you to clear collected values and restart aggregation. That might be useful, for example, after you have made a runtime configuration change. Exceptions to this truncation behavior are noted in individual summary table sections.

The following sections describe how to use specific tables to control Performance Schema pre-filtering.