PG_OPCLASS

PG_OPCLASS defines index access method operator classes.

Each operator class defines semantics for index columns of a particular data type and a particular index access method. An operator class essentially specifies that a particular operator family is applicable to a particular indexable column data type. The set of operators from the family that are actually usable with the indexed column are whichever ones accept the column's data type as their left-hand input.

Table 1 PG_OPCLASS columns

Name	Type	Reference	Description
oid	oid	-	Row identifier (hidden attribute, which must be specified)
opcmethod	oid	OID in PG_AM	Index access method operator class served by an operator class
opcname	name	-	Name of the operator class
opcnamespace	oid	OID in PG_NAMESPACE	Namespace of the operator class
opcowner	oid	OID in PG_AUTHID	Owner of the operator class
opcfamily	oid	OID in PG_OPFAMILY	Operator family containing the operator class
opcintype	oid	OID in PG_TYPE	Data type that the operator class indexes
opcdefault	boolean	-	The value is true if this operator class is the default for opcintype.
opckeytype	oid	OID in PG_TYPE	Type of data stored in an index, or zero if same as opcintype

An operator class's opcmethod must match the opfmethod of its containing operator family.