The catalog pg_index contains part of the information about indexes. The rest is mostly in pg_class .

Table 49-26. pg_index Columns

Name 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 int2 The number of columns in the index (duplicates pg_class.relnatts )
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 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.
indcollation oidvector pg_collation .oid For each column in the index key, this contains the OID of the collation to use for the index.
indclass oidvector pg_opclass .oid For each column in the index key, this contains the OID of the operator class to use. See pg_opclass for details.
indoption int2vector This is an array of indnatts 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.