---
title: "pg_index"
id: catalog-pg-index
pg_version: "20devel"
---

<a id="catalog-pg-index"></a>

## 52.26. pg_index

The catalog pg_index contains part of the information about indexes. The rest is mostly in [pg_class](catalog-pg-class.md). 

**pg_index Columns**

| Column Type | Description | 
| --- | --- |
| `indexrelid` `oid` (references [pg_class](catalog-pg-class.md).`oid`) | The OID of the [pg_class](catalog-pg-class.md) entry for this index |
| `indrelid` `oid` (references [pg_class](catalog-pg-class.md).`oid`) | The OID of the [pg_class](catalog-pg-class.md) 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 |
| `indnullsnotdistinct` `bool` | This value is only used for unique indexes. If false, this unique index will consider null values distinct (so the index can contain multiple null values in a column, the default PostgreSQL behavior). If it is true, it will consider null values to be equal (so the index can only contain one null value in a column). |
| `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`](sql-insert.md)/[`UPDATE`](sql-update.md) 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](storage-hot.md) 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`](sql-insert.md)/[`UPDATE`](sql-update.md) 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 ...`](sql-altertable.md#sql-altertable-replica-identity) |
| `indkey` `int2vector` (references [pg_attribute](catalog-pg-attribute.md).`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 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` (references [pg_collation](catalog-pg-collation.md).`oid`) | 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` (references [pg_opclass](catalog-pg-opclass.md).`oid`) | For each column in the index key (`indnkeyatts` values), this contains the OID of the operator class to use. See [pg_opclass](catalog-pg-opclass.md) 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. |