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MySQL 8.0 Reference Manual  /  ...  /  The INFORMATION_SCHEMA INNODB_INDEXES Table

Pre-General Availability Draft: 2017-12-15

25.32.22 The INFORMATION_SCHEMA INNODB_INDEXES Table

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”.

Table 25.22 INNODB_INDEXES Columns

Column nameDescription
INDEX_IDAn identifier for each index that is unique across all the databases in an instance.
NAMEThe name of the index. Most indexes created implicitly by InnoDB have consistent names but the index names are not necessarily unique. For example, 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_IDAn identifier representing the table associated with the index; the same value from INNODB_TABLES.TABLE_ID.
TYPEA numeric identifier signifying the kind of index. 0 = Secondary Index, 1 = Clustered Index, 2 = Unique Index, 3 = Primary Index, 32 = Full-text Index, 64 = Spatial Index, 128 = A secondary index that includes a virtual generated column.
N_FIELDSThe number of columns in the index key. For the GEN_CLUST_INDEX indexes, this value is 0 because the index is created using an artificial value rather than a real table column.
PAGE_NOThe root page number of the index B-tree. For full-text indexes, the PAGE_NO field is unused and set to -1 (FIL_NULL) because the full-text index is laid out in several B-trees (auxiliary tables).
SPACEAn identifier for the tablespace where the index resides. 0 means the InnoDB system tablespace. Any other number represents a table created in file-per-table mode with a separate .ibd file. 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_THRESHOLDThe 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 15.6.12, “Configuring the Merge Threshold for Index Pages”.

Example:

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_INDEXES WHERE TABLE_ID = 34\G
*************************** 1. row ***************************
       INDEX_ID: 39
           NAME: GEN_CLUST_INDEX
       TABLE_ID: 34
           TYPE: 1
       N_FIELDS: 0
        PAGE_NO: 3
          SPACE: 23
MERGE_THRESHOLD: 50
*************************** 2. row ***************************
       INDEX_ID: 40
           NAME: i1
       TABLE_ID: 34
           TYPE: 0
       N_FIELDS: 1
        PAGE_NO: 4
          SPACE: 23
MERGE_THRESHOLD: 50

Notes:

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

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


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