Movatterモバイル変換

CREATE OPERATOR

CREATE OPERATOR — define a new operator

Synopsis

CREATE OPERATORname (    PROCEDURE =function_name    [, LEFTARG =left_type ] [, RIGHTARG =right_type ]    [, COMMUTATOR =com_op ] [, NEGATOR =neg_op ]    [, RESTRICT =res_proc ] [, JOIN =join_proc ]    [, HASHES ] [, MERGES ])

Description

CREATE OPERATOR defines a new operator,name. The user who defines an operator becomes its owner. If a schema name is given then the operator is created in the specified schema. Otherwise it is created in the current schema.

The operator name is a sequence of up toNAMEDATALEN-1 (63 by default) characters from the following list:

There are a few restrictions on your choice of name:

The operator!= is mapped to<> on input, so these two names are always equivalent.

At least one ofLEFTARG andRIGHTARG must be defined. For binary operators, both must be defined. For right unary operators, onlyLEFTARG should be defined, while for left unary operators onlyRIGHTARG should be defined.

Thefunction_name procedure must have been previously defined usingCREATE FUNCTION and must be defined to accept the correct number of arguments (either one or two) of the indicated types.

The other clauses specify optional operator optimization clauses. Their meaning is detailed inSection 34.13.

To be able to create an operator, you must haveUSAGE privilege on the argument types and the return type, as well asEXECUTE privilege on the underlying function. If a commutator or negator operator is specified, you must own these operators.

Parameters

To give a schema-qualified operator name incom_op or the other optional arguments, use theOPERATOR() syntax, for example:

COMMUTATOR = OPERATOR(myschema.===) ,

Notes

Refer toSection 34.12 for further information.

It is not possible to specify an operator's lexical precedence inCREATE OPERATOR, because the parser's precedence behavior is hard-wired. SeeSection 4.1.6 for precedence details.

The obsolete optionsSORT1,SORT2,LTCMP, andGTCMP were formerly used to specify the names of sort operators associated with a merge-joinable operator. This is no longer necessary, since information about associated operators is found by looking at B-tree operator families instead. If one of these options is given, it is ignored except for implicitly settingMERGES true.

UseDROP OPERATOR to delete user-defined operators from a database. UseALTER OPERATOR to modify operators in a database.

Examples

The following command defines a new operator, area-equality, for the data typebox:

CREATE OPERATOR === (    LEFTARG = box,    RIGHTARG = box,    PROCEDURE = area_equal_procedure,    COMMUTATOR = ===,    NEGATOR = !==,    RESTRICT = area_restriction_procedure,    JOIN = area_join_procedure,    HASHES, MERGES);

Compatibility

CREATE OPERATOR is aPostgres Pro extension. There are no provisions for user-defined operators in the SQL standard.

See Also