create_operator_class

CREATE OPERATOR CLASS()		 SQL Commands	      CREATE OPERATOR CLASS()



NAME
       CREATE OPERATOR CLASS - define a new operator class


SYNOPSIS
       CREATE OPERATOR CLASS name [ DEFAULT ] FOR TYPE data_type USING index_method AS
	 {  OPERATOR strategy_number operator_name [ ( op_type, op_type ) ] [ RECHECK ]
	  | FUNCTION support_number funcname ( argument_type [, ...] )
	  | STORAGE storage_type
	 } [, ... ]


DESCRIPTION
       CREATE OPERATOR CLASS creates a new operator class.  An operator class
       defines how a particular data type can be  used	with  an  index.  The
       operator	 class	specifies that certain operators will fill particular
       roles or ‘‘strategies’’ for this data type and this index method.  The
       operator class also specifies the support procedures to be used by the
       index method when the operator class is selected for an index  column.
       All  the	 operators  and	 functions  used by an operator class must be
       defined before the operator class is created.

       If a schema name is given then the operator class is  created  in  the
       specified  schema. Otherwise it is created in the current schema.  Two
       operator classes in the same schema can have the	 same  name  only  if
       they are for different index methods.

       The  user  who defines an operator class becomes its owner. Presently,
       the creating user must be  a  superuser.	 (This	restriction  is	 made
       because	an  erroneous operator class definition could confuse or even
       crash the server.)

       CREATE OPERATOR CLASS does not presently check  whether	the  operator
       class  definition includes all the operators and functions required by
       the index method. It is the user’s responsibility to  define  a	valid
       operator class.

       Refer to [XRef to XINDEX] for further information.

PARAMETERS
       name   The  name	 of the operator class to be created. The name may be
	      schema-qualified.

       DEFAULT
	      If present, the operator class will become the default operator
	      class  for its data type. At most one operator class can be the
	      default for a specific data type and index method.

       data_type
	      The column data type that this operator class is for.

       index_method
	      The name of the index method this operator class is for.

       strategy_number
	      The index method’s strategy number for an	 operator  associated
	      with the operator class.

       operator_name
	      The  name	 (optionally schema-qualified) of an operator associ-
	      ated with the operator class.

       op_type
	      The operand data type(s) of an operator, or NONE to  signify  a
	      left-unary  or right-unary operator. The operand data types may
	      be omitted in the normal case where they are the	same  as  the
	      operator class’s data type.

       RECHECK
	      If  present,  the	 index is ‘‘lossy’’ for this operator, and so
	      the rows retrieved using the index must be rechecked to  verify
	      that  they  actually satisfy the qualification clause involving
	      this operator.

       support_number
	      The index method’s support  procedure  number  for  a  function
	      associated with the operator class.

       funcname
	      The name (optionally schema-qualified) of a function that is an
	      index method support procedure for the operator class.

       argument_types
	      The parameter data type(s) of the function.

       storage_type
	      The data type actually stored in the index.  Normally  this  is
	      the  same as the column data type, but some index methods (only
	      GiST at this writing) allow it to	 be  different.	 The  STORAGE
	      clause must be omitted unless the index method allows a differ-
	      ent type to be used.

       The OPERATOR, FUNCTION, and STORAGE clauses may appear in any order.


EXAMPLES
       The following example command defines a GiST index operator class  for
       the  data  type	_int4  (array of int4). See contrib/intarray/ for the
       complete example.

       CREATE OPERATOR CLASS gist__int_ops
	   DEFAULT FOR TYPE _int4 USING gist AS
	       OPERATOR	       3       &&,
	       OPERATOR	       6       =       RECHECK,
	       OPERATOR	       7       @,
	       OPERATOR	       8       ~,
	       OPERATOR	       20      @@ (_int4, query_int),
	       FUNCTION	       1       g_int_consistent (internal, _int4, int4),
	       FUNCTION	       2       g_int_union (bytea, internal),
	       FUNCTION	       3       g_int_compress (internal),
	       FUNCTION	       4       g_int_decompress (internal),
	       FUNCTION	       5       g_int_penalty (internal, internal, internal),
	       FUNCTION	       6       g_int_picksplit (internal, internal),
	       FUNCTION	       7       g_int_same (_int4, _int4, internal);


COMPATIBILITY
       CREATE OPERATOR CLASS is a PostgreSQL extension. There  is  no  CREATE
       OPERATOR CLASS statement in the SQL standard.

SEE ALSO
       ALTER  OPERATOR	CLASS  [alter_operator_class(7)], DROP OPERATOR CLASS
       [drop_operator_class(l)]



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