| --- |
| title: pg_index |
| --- |
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| The `pg_index` system catalog table contains part of the information about indexes. The rest is mostly in [pg\_class](pg_class.html#topic1). |
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| <a id="topic1__gq143898"></a> |
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| | column | type | references | description | |
| |------------------|------------|----------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| |
| | `indexrelid` | oid | pg\_class.oid | The OID of the pg\_class entry for this index. | |
| | `indrelid` | oid | pg\_class.oid | The OID of the pg\_class entry for the table this index is for. | |
| | `indnatts` | smallint | | The number of columns in the index (duplicates pg\_class.relnatts). | |
| | `indisunique` | boolean | | If true, this is a unique index. | |
| | `indisclustered` | boolean | | If true, the table was last clustered on this index via the `CLUSTER` command. | |
| | `indisvalid` | boolean | | 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. | |
| | `indkey` | int2vector | pg\_attribute.attnum | 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 key. A zero in this array indicates that the corresponding index attribute is an expression over the table columns, rather than a simple column reference. | |
| | `indclass` | oidvector | pg\_opclass.oid | For each column in the index key this contains the OID of the operator class to use. | |
| | `indexprs` | text | | 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` | text | | Expression tree (in `nodeToString()` representation) for partial index predicate. NULL if not a partial index. | |
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| : <span class="tablecap">Table 1. pg\_catalog.pg\_index</span> |
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