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Performance Schema table_io_waits_summary_by_index_usage Table

MariaDB starting with 10.0

The table_io_waits_summary_by_index_usage table, along with many other new Performance Schema tables, was added in MariaDB 10.0.

The table_io_waits_summary_by_index_usage table records table I/O waits by index.

Column	Description
`OBJECT_TYPE`	`TABLE` in the case of all indexes.
`OBJECT_SCHEMA`	Schema name.
`OBJECT_NAME`	Table name.
`INDEX_NAME`	Index name, or `PRIMARY` for the primary index, `NULL` for no index (inserts are counted in this case).
`COUNT_STAR`	Number of summarized events and the sum of the `x_READ` and `x_WRITE` columns.
`SUM_TIMER_WAIT`	Total wait time of the summarized events that are timed.
`MIN_TIMER_WAIT`	Minimum wait time of the summarized events that are timed.
`AVG_TIMER_WAIT`	Average wait time of the summarized events that are timed.
`MAX_TIMER_WAIT`	Maximum wait time of the summarized events that are timed.
`COUNT_READ`	Number of all read operations, and the sum of the equivalent `x_FETCH` columns.
`SUM_TIMER_READ`	Total wait time of all read operations that are timed.
`MIN_TIMER_READ`	Minimum wait time of all read operations that are timed.
`AVG_TIMER_READ`	Average wait time of all read operations that are timed.
`MAX_TIMER_READ`	Maximum wait time of all read operations that are timed.
`COUNT_WRITE`	Number of all write operations, and the sum of the equivalent `x_INSERT`, `x_UPDATE` and `x_DELETE` columns.
`SUM_TIMER_WRITE`	Total wait time of all write operations that are timed.
`MIN_TIMER_WRITE`	Minimum wait time of all write operations that are timed.
`AVG_TIMER_WRITE`	Average wait time of all write operations that are timed.
`MAX_TIMER_WRITE`	Maximum wait time of all write operations that are timed.
`COUNT_FETCH`	Number of all fetch operations.
`SUM_TIMER_FETCH`	Total wait time of all fetch operations that are timed.
`MIN_TIMER_FETCH`	Minimum wait time of all fetch operations that are timed.
`AVG_TIMER_FETCH`	Average wait time of all fetch operations that are timed.
`MAX_TIMER_FETCH`	Maximum wait time of all fetch operations that are timed.
`COUNT_INSERT`	Number of all insert operations.
`SUM_TIMER_INSERT`	Total wait time of all insert operations that are timed.
`MIN_TIMER_INSERT`	Minimum wait time of all insert operations that are timed.
`AVG_TIMER_INSERT`	Average wait time of all insert operations that are timed.
`MAX_TIMER_INSERT`	Maximum wait time of all insert operations that are timed.
`COUNT_UPDATE`	Number of all update operations.
`SUM_TIMER_UPDATE`	Total wait time of all update operations that are timed.
`MIN_TIMER_UPDATE`	Minimum wait time of all update operations that are timed.
`AVG_TIMER_UPDATE`	Average wait time of all update operations that are timed.
`MAX_TIMER_UPDATE`	Maximum wait time of all update operations that are timed.
`COUNT_DELETE`	Number of all delete operations.
`SUM_TIMER_DELETE`	Total wait time of all delete operations that are timed.
`MIN_TIMER_DELETE`	Minimum wait time of all delete operations that are timed.
`AVG_TIMER_DELETE`	Average wait time of all delete operations that are timed.
`MAX_TIMER_DELETE`	Maximum wait time of all delete operations that are timed.

You can TRUNCATE the table, which will reset all counters to zero. The table is also truncated if the table_io_waits_summary_by_table table is truncated.

If a table's index structure is changed, index statistics recorded in this table may also be reset.

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https://mariadb.com/kb/en/performance-schema-table_io_waits_summary_by_index_usage-table/