28.4.5 The INFORMATION_SCHEMA INNODB_CACHED_INDEXES Table

The INNODB_CACHED_INDEXES table reports the number of index pages cached in the InnoDB buffer pool for each index.

For related usage information and examples, see Section 17.15.5, “InnoDB INFORMATION_SCHEMA Buffer Pool Tables”.

The INNODB_CACHED_INDEXES table has these columns:

• SPACE_ID

  The tablespace ID.

• INDEX_ID

  An identifier for the index. Index identifiers are unique across all the databases in an instance.

• N_CACHED_PAGES

  The total number of index pages cached in the InnoDB buffer pool for a specific index since MySQL Server last started.

Examples

This query returns the number of index pages cached in the InnoDB buffer pool for a specific index:

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_CACHED_INDEXES WHERE INDEX_ID=65\G
*************************** 1. row ***************************
      SPACE_ID: 4294967294
      INDEX_ID: 65
N_CACHED_PAGES: 45

This query returns the number of index pages cached in the InnoDB buffer pool for each index, using the INNODB_INDEXES and INNODB_TABLES tables to resolve the table name and index name for each INDEX_ID value.

SELECT
  tables.NAME AS table_name,
  indexes.NAME AS index_name,
  cached.N_CACHED_PAGES AS n_cached_pages
FROM
  INFORMATION_SCHEMA.INNODB_CACHED_INDEXES AS cached,
  INFORMATION_SCHEMA.INNODB_INDEXES AS indexes,
  INFORMATION_SCHEMA.INNODB_TABLES AS tables
WHERE
  cached.INDEX_ID = indexes.INDEX_ID
  AND indexes.TABLE_ID = tables.TABLE_ID;

Notes

• You must have the PROCESS privilege to query this table.

• Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.