pg_opclass
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.
Table 1. pg_catalog.pg_opclass
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. |