mysql.index_stats Table

The mysql.index_stats table stores engine-independent index statistics, such as cardinality, used by the optimizer to plan query execution.

The mysql.index_stats table is one of three tables storing data used for Engine-independent table statistics. The others are mysql.column_stats and mysql.table_stats.

It is populated when the ANALYZE TABLE statement is run, although not by default. See Collecting Statistics with the ANALYZE TABLE Statement for details.

It is possible to manually update the table and, unlike most system tables, there are some scenarios where this could be useful. See Manual updates to statistics tables for details.

This table uses the Aria storage engine.

The mysql.index_stats table contains the following fields:

Field	Type	Null	Key	Default	Description
db_name	varchar(64)	NO	PRI	NULL	Database the table is in.
table_name	varchar(64)	NO	PRI	NULL	Table name
index_name	varchar(64)	NO	PRI	NULL	Name of the index
prefix_arity	int(11) unsigned	NO	PRI	NULL	Index prefix length. 1 for the first keypart, 2 for the first two, and so on. InnoDB's extended keys are supported.
avg_frequency	decimal(12,4)	YES		NULL	Average number of records one will find for given values of (keypart1, keypart2, ..), provided the values will be found in the table.

It is possible to manually update the table. See Manual updates to statistics tables for details.

_{This page is licensed: CC BY-SA / Gnu FDL}