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.
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.
