43.18. pg_index

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

Table 43-18. pg_index Columns

indexrelidoidpg_class.oidThe OID of the pg_class entry for this index
indrelidoidpg_class.oidThe OID of the pg_class entry for the table this index is for
indnattsint2 The number of columns in the index (duplicates pg_class.relnatts)
indisuniquebool If true, this is a unique index
indisprimarybool If true, this index represents the primary key of the table. (indisunique should always be true when this is true.)
indisclusteredbool If true, the table was last clustered on this index
indisvalidbool  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 true either
indkeyint2vectorpg_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.
indclassoidvectorpg_opclass.oid For each column in the index key this contains the OID of the operator class to use. See pg_opclass for details
indexprstext 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
indpredtext Expression tree (in nodeToString() representation) for partial index predicate. NULL if not a partial index