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CREATE OPERATOR CLASS

Name

CREATE OPERATOR CLASS  --  define a new operator class for indexes

Synopsis

CREATE OPERATOR CLASS name [ DEFAULT ] FOR TYPE data_type USING access_method AS
  {  OPERATOR strategy_number operator_id [ ( type, type ) ] [ RECHECK ]
   | FUNCTION support_number func_name ( parameter_types )
   | STORAGE storage_type
  } [, ... ]
  

Inputs

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 index operator class for its data type. At most one operator class can be the default for a specific data type and access method.

data_type

The column data type that this operator class is for.

access_method

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

strategy_number

The index access method's strategy number for an operator associated with the operator class.

operator_id

The identifier (optionally schema-qualified) of an operator associated with the operator class.

type

The input data type(s) of an operator, or NONE to signify a left-unary or right-unary operator. The input 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 tuples retrieved using the index must be rechecked to verify that they actually satisfy the qualification clause involving this operator.

support_number

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

func_name

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

parameter_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 access methods (only GIST at this writing) allow it to be different. The STORAGE clause must be omitted unless the index access method allows a different type to be used.

Outputs

CREATE OPERATOR CLASS

Message returned if the operator class is successfully created.

Description

CREATE OPERATOR CLASS defines a new operator class, name.

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 access method. The operator class also specifies the support procedures to be used by the index access 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 (the one at the front of the search path; see CURRENT_SCHEMA()). Two operator classes in the same schema can have the same name only if they are for different index access 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 class definition includes all the operators and functions required by the index access method. It is the user's responsibility to define a valid operator class.

Refer to the chapter on interfacing extensions to indexes in the PostgreSQL Programmer's Guide for further information.

Notes

Refer to DROP OPERATOR CLASS to delete user-defined operator classes from a database.

Usage

The following example command defines a GiST index operator class for 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);
  

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

Compatibility

SQL92

CREATE OPERATOR CLASS is a PostgreSQL extension. There is no CREATE OPERATOR CLASS statement in SQL92.

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