CREATE OPERATOR

CREATE OPERATOR

7

SQL - Language Statements

CREATE OPERATOR

define a new operator

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:

-   `--` 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 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.

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 [???](#xoper-optimization).

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 [???](#xoper) 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 [???](#sql-precedence) 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`](#sql-dropoperator) to delete user-defined
operators from a database. Use [`ALTER OPERATOR`](#sql-alteroperator) 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
========
