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mysql.innodb_index_stats

The mysql.innodb_index_stats table stores data related to particular InnoDB Persistent Statistics, and contains multiple rows for each index.

This table, along with the related mysql.innodb_table_stats table, can be manually updated in order to force or test differing query optimization plans. After updating, FLUSH TABLE innodb_index_stats is required to load the changes.

mysql.innodb_index_stats is not replicated, although any ANALYZE TABLE statements on the table will be by default..

It contains the following fields:

Field Type Null Key Default Description
database_name varchar(64) NO PRI NULL Database name.
table_name varchar(64) NO PRI NULL Table, partition or subpartition name.
index_name varchar(64) NO PRI NULL Index name.
last_update timestamp NO current_timestamp() Time that this row was last updated.
stat_name varchar(64) NO PRI NULL Statistic name.
stat_value bigint(20) unsigned NO NULL Estimated statistic value.
sample_size bigint(20) unsigned YES NULL Number of pages sampled for the estimated statistic value.
stat_description varchar(1024) NO NULL Statistic description.

Example

SELECT * FROM mysql.innodb_index_stats\G
*************************** 1. row ***************************
   database_name: mysql
      table_name: gtid_slave_pos
      index_name: PRIMARY
     last_update: 2017-08-19 20:38:34
       stat_name: n_diff_pfx01
      stat_value: 0
     sample_size: 1
stat_description: domain_id
*************************** 2. row ***************************
   database_name: mysql
      table_name: gtid_slave_pos
      index_name: PRIMARY
     last_update: 2017-08-19 20:38:34
       stat_name: n_diff_pfx02
      stat_value: 0
     sample_size: 1
stat_description: domain_id,sub_id
*************************** 3. row ***************************
   database_name: mysql
      table_name: gtid_slave_pos
      index_name: PRIMARY
     last_update: 2017-08-19 20:38:34
       stat_name: n_leaf_pages
      stat_value: 1
     sample_size: NULL
stat_description: Number of leaf pages in the index
*************************** 4. row ***************************
   database_name: mysql
      table_name: gtid_slave_pos
      index_name: PRIMARY
     last_update: 2017-08-19 20:38:34
       stat_name: size
      stat_value: 1
     sample_size: NULL
stat_description: Number of pages in the index
*************************** 5. row ***************************
   database_name: test
      table_name: ft
      index_name: FTS_DOC_ID_INDEX
     last_update: 2017-09-15 12:58:39
       stat_name: n_diff_pfx01
      stat_value: 0
     sample_size: 1
stat_description: FTS_DOC_ID
*************************** 6. row ***************************
   database_name: test
      table_name: ft
      index_name: FTS_DOC_ID_INDEX
     last_update: 2017-09-15 12:58:39
       stat_name: n_leaf_pages
      stat_value: 1
     sample_size: NULL
stat_description: Number of leaf pages in the index
...

See Also

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https://mariadb.com/kb/en/mysqlinnodb_index_stats/