CREATE OPERATOR(7) PostgreSQL 17.4 Documentation CREATE OPERATOR(7)
NAME
CREATE_OPERATOR - define a new operator
SYNOPSIS
CREATE OPERATOR name (
{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:
o -- and /* cannot appear anywhere in an operator name, since they
will be taken as the start of a comment.
o 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.
o 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 attributes.
Their meaning is detailed in Section 36.15.
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 those 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 36.14 and Section 36.15 for further information.
When you are defining a self-commutative operator, you just do it. When
you are defining a pair of commutative operators, things are a little
trickier: how can the first one to be defined refer to the other one,
which you haven't defined yet? There are three solutions to this
problem:
o One way is to omit the COMMUTATOR clause in the first operator that
you define, and then provide one in the second operator's
definition. Since PostgreSQL knows that commutative operators come
in pairs, when it sees the second definition it will automatically
go back and fill in the missing COMMUTATOR clause in the first
definition.
o Another, more straightforward way is just to include COMMUTATOR
clauses in both definitions. When PostgreSQL processes the first
definition and realizes that COMMUTATOR refers to a nonexistent
operator, the system will make a dummy entry for that operator in
the system catalog. This dummy entry will have valid data only for
the operator name, left and right operand types, and owner, since
that's all that PostgreSQL can deduce at this point. The first
operator's catalog entry will link to this dummy entry. Later, when
you define the second operator, the system updates the dummy entry
with the additional information from the second definition. If you
try to use the dummy operator before it's been filled in, you'll
just get an error message.
o Alternatively, both operators can be defined without COMMUTATOR
clauses and then ALTER OPERATOR can be used to set their commutator
links. It's sufficient to ALTER either one of the pair.
In all three cases, you must own both operators in order to mark them
as commutators.
Pairs of negator operators can be defined using the same methods as for
commutator pairs.
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.
SEE ALSO
ALTER OPERATOR (ALTER_OPERATOR(7)), CREATE OPERATOR CLASS
(CREATE_OPERATOR_CLASS(7)), DROP OPERATOR (DROP_OPERATOR(7))
PostgreSQL 17.4 2025 CREATE OPERATOR(7)
postgresql 17.4 - Generated Sat Mar 22 13:50:59 CDT 2025