CREATE OPERATOR — define a new operator
CREATE OPERATORname( {FUNCTION|PROCEDURE} =function_name[, LEFTARG =left_type] [, RIGHTARG =right_type] [, COMMUTATOR =com_op] [, NEGATOR =neg_op] [, RESTRICT =res_proc] [, JOIN =join_proc] [, HASHES ] [, MERGES ] )
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:
-- 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 allows PostgreSQL to parse SQL-compliant commands without requiring spaces between tokens.
The symbol => is reserved by the SQL grammar, so it cannot be used as an operator name.
The operator != is mapped to <> on input, so these two names are always equivalent.
For binary operators, both LEFTARG and RIGHTARG must be defined. For prefix operators only RIGHTARG should be defined. The function_name function 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.
In the syntax of CREATE OPERATOR, the keywords FUNCTION and PROCEDURE are equivalent, but the referenced function must in any case be a function, not a procedure. The use of the keyword PROCEDURE here is historical and deprecated.
The other clauses specify optional operator optimization clauses. Their meaning is detailed in Section 38.15.
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.
nameThe 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.
function_nameThe function used to implement this operator.
left_typeThe data type of the operator's left operand, if any. This option would be omitted for a prefix operator.
right_typeThe data type of the operator's right operand.
com_opThe commutator of this operator.
neg_opThe negator of this operator.
res_procThe restriction selectivity estimator function for this operator.
join_procThe join selectivity estimator function for this operator.
HASHESIndicates this operator can support a hash join.
MERGESIndicates this operator can support a merge join.
To give a schema-qualified operator name in com_op or the other optional arguments, use the OPERATOR() syntax, for example:
COMMUTATOR = OPERATOR(myschema.===) ,
Refer to Section 38.14 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.
The following command defines a new operator, area-equality, for the data type box:
CREATE OPERATOR === (
LEFTARG = box,
RIGHTARG = box,
FUNCTION = area_equal_function,
COMMUTATOR = ===,
NEGATOR = !==,
RESTRICT = area_restriction_function,
JOIN = area_join_function,
HASHES, MERGES
);
CREATE OPERATOR is a PostgreSQL extension. There are no provisions for user-defined operators in the SQL standard.
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