CREATE 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:
-- and/* cannot appear anywhere in an operator name, since they will be taken as the start of a comment.
A multicharacter operator name cannot end in+ or-, unless the name also contains at least one of these characters:
~ ! @ # % ^ & | ` ? For example,@- is an allowed operator name, but*- is not. This restriction allowsPostgreSQL to parse SQL-compliant commands without requiring spaces between tokens.
The use of=> as an operator name is deprecated. It may be disallowed altogether in a future release.
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 35.13.
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
- name
The name of the operator to be defined. See above for allowable characters. The name can be schema-qualified, for exampleCREATE 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 calledoverloading.
- function_name
The function used to implement this operator.
- left_type
The data type of the operator's left operand, if any. This option would be omitted for a left-unary operator.
- right_type
The data type of the operator's right operand, if any. This option would be omitted for a right-unary operator.
- com_op
The commutator of this operator.
- neg_op
The negator of this operator.
- res_proc
The restriction selectivity estimator function for this operator.
- join_proc
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 incom_op or the other optional arguments, use theOPERATOR() syntax, for example:
COMMUTATOR = OPERATOR(myschema.===) ,
Notes
Refer toSection 35.12 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);