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.

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