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
PG_AM.oid | Index access method operator class served by an operator class | ||
PG_NAMESPACE.oid | |||
PG_AUTHID.oid | |||
PG_OPFAMILY.oid | |||
PG_TYPE.oid | |||
The value is true if this operator class is the default for opcintype. | |||
PG_TYPE.oid |
An operator class's opcmethod must match the opfmethod of its containing operator family. There must be no more than one PG_OPCLASS row with opcdefault set to true for any given combination of opcmethod and opcintype.