Performance Schema Summary Tables •Index on ( EVENT_NAME ) • table_io_waits_summary_by_index_usage : Table I/O waits per index • table_io_waits_summary_by_table : Table I/O waits per table • table_lock_waits_summary_by_table : Table lock waits per table • COUNT_INSERT ,  SUM_TIMER_INSERT ,  MIN_TIMER_INSERT ,  AVG_TIMER_INSERT , MAX_TIMER_INSERT • COUNT_FETCH ,  SUM_TIMER_FETCH ,  MIN_TIMER_FETCH ,  AVG_TIMER_FETCH ,  MAX_TIMER_FETCH • COUNT_WRITE ,  SUM_TIMER_WRITE ,  MIN_TIMER_WRITE ,  AVG_TIMER_WRITE ,  MAX_TIMER_WRITE • COUNT_READ ,  SUM_TIMER_READ ,  MIN_TIMER_READ ,  AVG_TIMER_READ ,  MAX_TIMER_READ • COUNT_STAR ,  SUM_TIMER_WAIT ,  MIN_TIMER_WAIT ,  AVG_TIMER_WAIT ,  MAX_TIMER_WAIT 5065 These columns aggregate all fetch operations. These columns aggregate all write operations. They are the same as the sum of the corresponding xxx _INSERT ,  xxx _UPDATE , and  xxx _DELETE  columns. These columns aggregate all read operations. They are the same as the sum of the corresponding xxx _FETCH  columns. These columns aggregate all I/O operations. They are the same as the sum of the corresponding xxx _READ  and  xxx _WRITE  columns. table_io_waits_summary_by_table  has the following summary columns containing aggregated values. As indicated in the column descriptions, some columns are more general and have values that are the same as the sum of the values of more fine-grained columns. For example, columns that aggregate all writes hold the sum of the corresponding columns that aggregate inserts, updates, and deletes. In this way, aggregations at higher levels are available directly without the need for user-defined views that sum lower- level columns. The  table_io_waits_summary_by_table  table has these grouping columns to indicate how the table aggregates events:  OBJECT_TYPE ,  OBJECT_SCHEMA , and  OBJECT_NAME . These columns have the same meaning as in the  events_waits_current  table. They identify the table to which the row applies. The  table_io_waits_summary_by_table  table aggregates all table I/O wait events, as generated by the  wait/io/table/sql/handler  instrument. The grouping is by table. The table_io_waits_summary_by_table Table 27.12.20.8 Table I/O and Lock Wait Summary Tables The following sections describe the table I/O and lock wait summary tables: The MySQL server uses several techniques to avoid I/O operations by caching information read from files, so it is possible that statements you might expect to result in I/O events do not do so. You may be able to ensure that I/O does occur by flushing caches or restarting the server to reset its state. TRUNCATE TABLE  is permitted for file I/O summary tables. It resets the summary columns to zero rather than removing rows.