Performance Schema Summary Tables The total wait time of the summarized timed events. This value is calculated only for timed events because nontimed events have a wait time of  NULL . The same is true for the other  xxx _TIMER_WAIT values. The minimum wait time of the summarized timed events. The average wait time of the summarized timed events. The maximum wait time of the summarized timed events. The wait event summary tables have these indexes: TRUNCATE TABLE  is permitted for wait summary tables. It has these effects: In addition, each wait 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_waits_summary_global_by_event_name . For details, see Section 27.12.8, “Performance Schema Connection Tables” . 27.12.20.2 Stage Summary Tables 5052 •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. •For summary tables not aggregated by account, host, or user, truncation resets the summary columns to zero rather than removing rows. • events_waits_summary_by_account_by_event_name : •Primary key on ( USER ,  HOST ,  EVENT_NAME ) • events_waits_summary_by_host_by_event_name : •Primary key on ( HOST ,  EVENT_NAME ) • events_waits_summary_by_instance : •Primary key on ( OBJECT_INSTANCE_BEGIN ) •Index on ( EVENT_NAME ) • events_waits_summary_by_thread_by_event_name : •Primary key on ( THREAD_ID ,  EVENT_NAME ) • events_waits_summary_by_user_by_event_name : •Primary key on ( USER ,  EVENT_NAME ) • events_waits_summary_global_by_event_name : •Primary key on ( EVENT_NAME ) • MIN_TIMER_WAIT • AVG_TIMER_WAIT • MAX_TIMER_WAIT