CREATE OPERATOR (original) (raw)

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CREATE OPERATOR — define a new operator

Synopsis

CREATE OPERATOR name ( PROCEDURE = functionname [, LEFTARG = lefttype ] [, RIGHTARG = righttype ] [, COMMUTATOR = comop ] [, NEGATOR = negop ] [, RESTRICT = resproc ] [, JOIN = joinproc ] [, 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 to NAMEDATALEN-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 of LEFTARG and RIGHTARG must be defined. For binary operators, both must be defined. For right unary operators, only LEFTARG should be defined, while for left unary operators only RIGHTARG should be defined.

Note

Right unary, also called postfix, operators are deprecated and will be removed in PostgreSQL version 14.

The functionname procedure must have been previously defined using CREATE 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 in Section 37.13.

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

Parameters

name

The name of the operator to be defined. See above for allowable characters. The name can be schema-qualified, for example CREATE OPERATOR myschema.+ (...). If not, then the operator is created in the current schema. Two operators in the same schema can have the same name if they operate on different data types. This is called overloading.

functionname

The function used to implement this operator.

lefttype

The data type of the operator's left operand, if any. This option would be omitted for a left-unary operator.

righttype

The data type of the operator's right operand, if any. This option would be omitted for a right-unary operator.

comop

The commutator of this operator.

negop

The negator of this operator.

resproc

The restriction selectivity estimator function for this operator.

joinproc

The join selectivity estimator function for this operator.

HASHES

Indicates this operator can support a hash join.

MERGES

Indicates this operator can support a merge join.

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

COMMUTATOR = OPERATOR(myschema.===) ,

Notes

Refer to Section 37.12 for further information.

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

The obsolete options SORT1, SORT2, LTCMP, and GTCMP 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 setting MERGES true.

Use DROP OPERATOR to delete user-defined operators from a database. Use ALTER OPERATOR to modify operators in a database.

Examples

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

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 a PostgreSQL extension. There are no provisions for user-defined operators in the SQL standard.