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25.39.19 The INFORMATION_SCHEMA INNODB_INDEXES Table

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The INNODB_INDEXES table provides metadata about InnoDB indexes.

For related usage information and examples, see Section 15.14.3, “InnoDB INFORMATION_SCHEMA Schema Object Tables”.

The INNODB_INDEXES table has these columns:

  • INDEX_ID

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

  • NAME

    The name of the index. Most indexes created implicitly by InnoDB have consistent names but the index names are not necessarily unique. Examples: PRIMARY for a primary key index, GEN_CLUST_INDEX for the index representing a primary key when one is not specified, and ID_IND, FOR_IND, and REF_IND for foreign key constraints.

  • TABLE_ID

    An identifier representing the table associated with the index; the same value as INNODB_TABLES.TABLE_ID.

  • TYPE

    A numeric value derived from bit-level information that identifies the index type. 0 = nonunique secondary index; 1 = automatically generated clustered index (GEN_CLUST_INDEX); 2 = unique nonclustered index; 3 = clustered index; 32 = full-text index; 64 = spatial index; 128 = secondary index on a virtual generated column.

  • N_FIELDS

    The number of columns in the index key. For GEN_CLUST_INDEX indexes, this value is 0 because the index is created using an artificial value rather than a real table column.

  • PAGE_NO

    The root page number of the index B-tree. For full-text indexes, the PAGE_NO column is unused and set to -1 (FIL_NULL) because the full-text index is laid out in several B-trees (auxiliary tables).

  • SPACE

    An identifier for the tablespace where the index resides. 0 means the InnoDB system tablespace. Any other number represents a table created with a separate .ibd file in file-per-table mode. This identifier stays the same after a TRUNCATE TABLE statement. Because all indexes for a table reside in the same tablespace as the table, this value is not necessarily unique.

  • MERGE_THRESHOLD

    The merge threshold value for index pages. If the amount of data in an index page falls below the MERGE_THRESHOLD value when a row is deleted or when a row is shortened by an update operation, InnoDB attempts to merge the index page with the neighboring index page. The default threshold value is 50%. For more information, see Section 15.8.11, “Configuring the Merge Threshold for Index Pages”.

Example

  1. mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_INDEXES WHERE TABLE_ID = 34\G
  2. *************************** 1. row ***************************
  3.        INDEX_ID: 39
  4.            NAME: GEN_CLUST_INDEX
  5.        TABLE_ID: 34
  6.            TYPE: 1
  7.        N_FIELDS: 0
  8.         PAGE_NO: 3
  9.           SPACE: 23
  10. MERGE_THRESHOLD: 50
  11. *************************** 2. row ***************************
  12.        INDEX_ID: 40
  13.            NAME: i1
  14.        TABLE_ID: 34
  15.            TYPE: 0
  16.        N_FIELDS: 1
  17.         PAGE_NO: 4
  18.           SPACE: 23
  19. MERGE_THRESHOLD: 50

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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.


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Document created the 26/06/2006, last modified the 26/10/2018
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