51.26. pg_index
The catalog pg_index contains part of the information about indexes. The rest is mostly in pg_class.
Table 51.26. pg_index Columns
| Name | Type | References | Description |
|---|---|---|---|
indexrelid | oid | | The OID of the pg_class entry for this index |
indrelid | oid | | The OID of the pg_class entry for the table this index is for |
indnatts | int2 | The total number of columns in the index (duplicates pg_class.relnatts); this number includes both key and included attributes | |
indnkeyatts | int2 | The number of key columns in the index, not counting any included columns, which are merely stored and do not participate in the index semantics | |
indisunique | bool | If true, this is a unique index | |
indisprimary | bool | If true, this index represents the primary key of the table (indisunique should always be true when this is true) | |
indisexclusion | bool | If true, this index supports an exclusion constraint | |
indimmediate | bool | If true, the uniqueness check is enforced immediately on insertion (irrelevant if indisunique is not true) | |
indisclustered | bool | If true, the table was last clustered on this index | |
indisvalid | bool | If true, the index is currently valid for queries. False means the index is possibly incomplete: it must still be modified by INSERT/UPDATE operations, but it cannot safely be used for queries. If it is unique, the uniqueness property is not guaranteed true either. | |
indcheckxmin | bool | If true, queries must not use the index until the xmin of this pg_index row is below their TransactionXmin event horizon, because the table may contain broken HOT chains with incompatible rows that they can see | |
indisready | bool | If true, the index is currently ready for inserts. False means the index must be ignored by INSERT/UPDATE operations. | |
indislive | bool | If false, the index is in process of being dropped, and should be ignored for all purposes (including HOT-safety decisions) | |
indisreplident | bool | If true this index has been chosen as “replica identity” using ALTER TABLE ... REPLICA IDENTITY USING INDEX ... | |
indkey | int2vector | | This is an array of indnatts values that indicate which table columns this index indexes. For example a value of 1 3 would mean that the first and the third table columns make up the index entries. Key columns come before non-key (included) columns. A zero in this array indicates that the corresponding index attribute is an expression over the table columns, rather than a simple column reference. |
indcollation | oidvector | | For each column in the index key (indnkeyatts values), this contains the OID of the collation to use for the index, or zero if the column is not of a collatable data type. |
indclass | oidvector | | For each column in the index key (indnkeyatts values), this contains the OID of the operator class to use. See pg_opclass for details. |
indoption | int2vector | This is an array of indnkeyatts values that store per-column flag bits. The meaning of the bits is defined by the index's access method. | |
indexprs | pg_node_tree | Expression trees (in nodeToString() representation) for index attributes that are not simple column references. This is a list with one element for each zero entry in indkey. Null if all index attributes are simple references. | |
indpred | pg_node_tree | Expression tree (in nodeToString() representation) for partial index predicate. Null if not a partial index. |