create_operator

CREATE OPERATOR()		 SQL Commands		    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  opera-
       tor 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	with-
	 out 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 oper-
       ators,  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 [XRef to XOPER].

PARAMETERS
       name   The name of the operator to be defined. See above for allowable
	      characters.  The name may be schema-qualified, for example CRE-
	      ATE 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 opera-
	      tor.

       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 opera-
	      tor that sorts the left-hand data type of this operator.

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

       less_than_op
	      If this operator can support a merge join, the less-than opera-
	      tor 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 [XRef to XOPER] 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.



SQL - Language Statements	  2008-01-03		    CREATE OPERATOR()