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 

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 *************************** 

