PG_INDEX

PG_INDEX records part of the information about indexes. The rest is mostly in PG_CLASS.

**Table 1** PG_INDEX columns
Name	Type	Description
indexrelid	oid	OID of the pg_class entry for this index
indrelid	oid	OID of the pg_class entry for the table this index is for
indnatts	smallint	Number of columns in an index
indisunique	boolean	This index is a unique index if the value is true.
indisprimary	boolean	This index represents the primary key of the table if the value is true. If this value is true, the value of indisunique is true.
indisexclusion	boolean	This index supports exclusion constraints if the value is true.
indimmediate	boolean	A uniqueness check is performed upon data insertion if the value is true.
indisclustered	boolean	The table was last clustered on this index if the value is true.
indisusable	boolean	This index supports insert/select if the value is true.
indisvalid	boolean	This index is valid for queries if the value is true. If this column is false, this index is possibly incomplete and must still be modified by INSERT/UPDATE operations, but it cannot safely be used for queries. If it is a unique index, the uniqueness property is also not true.
indcheckxmin	boolean	If the value is true, queries must not use the index until the xmin of this row in pg_index is below their TransactionXmin event horizon, because the table may contain broken HOT chains with incompatible rows that they can see.
indisready	boolean	If the value is true, this index is ready for inserts. If the value is false, this index is ignored when data is inserted or modified.
indkey	int2vector	This is an array of indnatts values that indicate which table columns this index creates. For example, a value of 1 3 means that the first and the third columns make up the index key. 0 in this array indicates that the corresponding index attribute is an expression over the table columns, rather than a simple column reference.
indcollation	oidvector	ID of each column used by the index
indclass	oidvector	For each column in the index key, this column contains the OID of the operator class to use. For details, see PG_OPCLASS.
indoption	int2vector	Array of 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. It 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. If the index is not a partial index, the value is null.