CREATE OPERATOR
CREATE OPERATOR
CREATE OPERATOR - define a new operator
Synopsis
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 ] )
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:
-
--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.
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 . -
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 prefix operator.
-
right_type -
The data type of the operator's right operand.
-
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 in
com_op
or the other optional
arguments, use the
OPERATOR()
syntax, for example:
COMMUTATOR = OPERATOR(myschema.===) ,
Notes
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.
Examples
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
);
Compatibility
CREATE OPERATOR
is a
PostgreSQL
extension. There are no
provisions for user-defined operators in the SQL standard.