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The pg_opclass system catalog table 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. Note that there can be multiple operator classes for a given data type/access method combination, thus supporting multiple behaviors. The majority of the information defining an operator class is actually not in its pg_opclass row, but in the associated rows in pg_amop and pg_amproc. Those rows are considered to be part of the operator class definition — this is not unlike the way that a relation is defined by a single pg_class row plus associated rows in pg_attribute and other tables.
| column | type | references | description |
|---|---|---|---|
opcamid | oid | pg_am.oid | Index access method operator class is for. |
opcname | name | Name of this operator class | |
opcnamespace | oid | pg_namespace.oid | Namespace of this operator class |
opcowner | oid | pg_authid.oid | Owner of the operator class |
opcintype | oid | pg_type.oid | Data type that the operator class indexes. |
opcdefault | boolean | True if this operator class is the default for the data type opcintype. | |
opckeytype | oid | pg_type.oid | Type of data stored in index, or zero if same as opcintype. |
Parent topic: System Catalogs Definitions
