45.27. pg_opclass

The catalog 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 lefthand input.

Operator classes are described at length in Section 35.14.

Table 45-27. pg_opclass Columns

NameTypeReferencesDescription
opcmethodoidpg_am.oidIndex access method operator class is for
opcnamename Name of this operator class
opcnamespaceoidpg_namespace.oidNamespace of this operator class
opcowneroidpg_authid.oidOwner of the operator class
opcfamilyoidpg_opfamily.oidOperator family containing the operator class
opcintypeoidpg_type.oidData type that the operator class indexes
opcdefaultbool True if this operator class is the default for opcintype
opckeytypeoidpg_type.oidType of data stored in index, or zero if same as opcintype

An operator class's opcmethod must match the opfmethod of its containing operator family. Also, there must be no more than one pg_opclass row having opcdefault true for any given combination of opcmethod and opcintype.