52.33. 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 left-hand input.

   Operator classes are described at length in Section 36.16.

   Table 52.33. pg_opclass Columns

   Column Type

   Description

   oid oid

   Row identifier

   opcmethod oid (references pg_am.oid)

   Index access method operator class is for

   opcname name

   Name of this operator class

   opcnamespace oid (references pg_namespace.oid)

   Namespace of this operator class

   opcowner oid (references pg_authid.oid)

   Owner of the operator class

   opcfamily oid (references pg_opfamily.oid)

   Operator family containing the operator class

   opcintype oid (references pg_type.oid)

   Data type that the operator class indexes

   opcdefault bool

   True if this operator class is the default for opcintype

   opckeytype oid (references pg_type.oid)

   Type 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.