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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 operator
       is created in the specified schema. Otherwise it is created in the cur-
       rent 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 opera-
       tors,  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 the documentation.

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  data	 type  of  the	operator's left operand, if any.  This
	      option would be omitted for a left-unary operator.

       righttype
	      The data type of the operator's right  operand,  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 the documentation for further information.

       Use  DROP  OPERATOR [drop_operator(7)] to delete user-defined operators
       from a database. Use ALTER OPERATOR [alter_operator(7)] to modify oper-
       ators in 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.

SEE ALSO
       ALTER OPERATOR [alter_operator(7)], CREATE OPERATOR CLASS [create_oper-
       ator_class(l)], DROP OPERATOR [drop_operator(l)]



SQL - Language Statements	  2010-12-14		     CREATE OPERATOR()
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