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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/