Event Pre-Filtering •To use the Performance Schema to investigate a performance issue when the restrictions to impose using pre-filtering are not known in advance. •To configure pre-filtering at the producer stage, several tables can be used: • setup_instruments  indicates which instruments are available. An instrument disabled in this table produces no events regardless of the contents of the other production-related setup tables. An instrument enabled in this table is permitted to produce events, subject to the contents of the other tables. • setup_objects  controls whether the Performance Schema monitors particular table and stored program objects. • threads  indicates whether monitoring is enabled for each server thread. • setup_actors  determines the initial monitoring state for new foreground threads. •To configure pre-filtering at the consumer stage, modify the  setup_consumers  table. This determines the destinations to which events are sent.  setup_consumers  also implicitly affects event production. If a given event is not sent to any destination (that is, it is never consumed), the Performance Schema does not produce it. 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. The  setup_instruments  table lists the available instruments: The following sections provide more detail about pre-filtering and provide guidelines for naming instruments or consumers in filtering operations. For information about writing queries to retrieve information (post-filtering), see Section 27.5, “Performance Schema Queries” . 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: 27.4.3 Event Pre-Filtering 27.4.4 Pre-Filtering by Instrument 4909 mysql>  SELECT NAME, ENABLED, TIMED FROM performance_schema.setup_instruments; +---------------------------------------------------+---------+-------+ | NAME | ENABLED | TIMED | +---------------------------------------------------+---------+-------+