Performance Schema Summary Tables •Primary key on ( HOST ,  EVENT_NAME ) • events_stages_summary_by_thread_by_event_name : •Primary key on ( THREAD_ID ,  EVENT_NAME ) • events_stages_summary_by_user_by_event_name : •Primary key on ( USER ,  EVENT_NAME ) • events_stages_summary_global_by_event_name : •Primary key on ( EVENT_NAME ) TRUNCATE TABLE  is permitted for stage summary tables. It has these effects: •For summary tables not aggregated by account, host, or user, truncation resets the summary columns to zero rather than removing rows. •For summary tables aggregated by account, host, or user, truncation removes rows for accounts, hosts, or users with no connections, and resets the summary columns to zero for the remaining rows. In addition, each stage summary table that is aggregated by account, host, user, or thread is implicitly truncated by truncation of the connection table on which it depends, or truncation of events_stages_summary_global_by_event_name . For details, see Section 27.12.8, “Performance Schema Connection Tables” . The Performance Schema maintains tables for collecting current and recent statement events, and aggregates that information in summary tables. Section 27.12.6, “Performance Schema Statement Event Tables”  describes the events on which statement summaries are based. See that discussion for information about the content of statement events, the current and historical statement event tables, and how to control statement event collection, which is partially disabled by default. Example statement event summary information: 27.12.20.3 Statement Summary Tables 5054 mysql>  SELECT * FROM performance_schema.events_statements_summary_global_by_event_name\G *************************** 1. row *************************** EVENT_NAME: statement/sql/select COUNT_STAR: 25 SUM_TIMER_WAIT: 1535983999000 MIN_TIMER_WAIT: 209823000 AVG_TIMER_WAIT: 61439359000 MAX_TIMER_WAIT: 1363397650000 SUM_LOCK_TIME: 20186000000 SUM_ERRORS: 0 SUM_WARNINGS: 0 SUM_ROWS_AFFECTED: 0 SUM_ROWS_SENT: 388 SUM_ROWS_EXAMINED: 370 SUM_CREATED_TMP_DISK_TABLES: 0 SUM_CREATED_TMP_TABLES: 0 SUM_SELECT_FULL_JOIN: 0  SUM_SELECT_FULL_RANGE_JOIN: 0 SUM_SELECT_RANGE: 0 SUM_SELECT_RANGE_CHECK: 0 SUM_SELECT_SCAN: 6 SUM_SORT_MERGE_PASSES: 0