PostgreSQL 7.4.3 Documentation
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# CREATE OPERATOR

## Name

CREATE OPERATOR -- define a new operator

## Synopsis

    CREATE OPERATOR name (
        PROCEDURE = funcname
        [, LEFTARG = lefttype ] [, RIGHTARG = righttype ]
        [, COMMUTATOR = com_op ] [, NEGATOR = neg_op ]
        [, RESTRICT = res_proc ] [, JOIN = join_proc ]
        [, HASHES ] [, MERGES ]
        [, SORT1 = left_sort_op ] [, SORT2 = right_sort_op ]
        [, LTCMP = less_than_op ] [, GTCMP = greater_than_op ]
    )

## 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 operator `!=` is mapped to `<>` on input, so these two names are always equivalent.

At least one of `LEFTARG` and `RIGHTARG` must be defined. For binary operators, both must be defined. For right unary operators, only `LEFTARG` should be defined, while for left unary operators only `RIGHTARG` should be defined.

The funcname procedure 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.

The other clauses specify optional operator optimization clauses. Their meaning is detailed in Section 33.11.

## Parameters

name

  The name of the operator to be defined. See above for allowable characters. The name may 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.

funcname

  The function used to implement this operator.

lefttype

  The type of the left-hand argument of the operator, if any. This option would be omitted for a left-unary operator.

righttype

  The type of the right-hand argument of the operator, 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.

left_sort_op

  If this operator can support a merge join, the less-than operator that sorts the left-hand data type of this operator.

right_sort_op

  If this operator can support a merge join, the less-than operator that sorts the right-hand data type of this operator.

less_than_op

  If this operator can support a merge join, the less-than operator that compares the input data types of this operator.

greater_than_op

  If this operator can support a merge join, the greater-than operator that compares the input data types of this operator.

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 33.11 for further information.

Use `DROP OPERATOR` to delete user-defined operators from a database.

## Examples

The following command defines a new operator, area-equality, for the data type `box`:

    CREATE OPERATOR === (
        LEFTARG = box,
        RIGHTARG = box,
        PROCEDURE = area_equal_procedure,
        COMMUTATOR = ===,
        NEGATOR = !==,
        RESTRICT = area_restriction_procedure,
        JOIN = area_join_procedure,
        HASHES,
        SORT1 = <<<,
        SORT2 = <<<
        -- Since sort operators were given, MERGES is implied.
        -- LTCMP and GTCMP are assumed to be < and > respectively
    );

## Compatibility

`CREATE OPERATOR` is a PostgreSQL extension. There are no provisions for user-defined operators in the SQL standard.

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