CREATE OPERATOR CLASS

CREATE OPERATOR CLASS

7

SQL - Language Statements

CREATE OPERATOR CLASS

define a new operator class

CREATE OPERATOR CLASS

name

\[ DEFAULT \] FOR TYPE

data\_type

USING

index\_method

\[ FAMILY

family\_name

\] AS { OPERATOR

strategy\_number

operator\_name

\[ (

op\_type

,

op\_type

) \] \[ FOR SEARCH \| FOR ORDER BY

sort\_family\_name

\] \| FUNCTION

support\_number

\[ (

op\_type

\[ ,

op\_type

\] ) \]

function\_name

(

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 functions 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 can be 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, nor whether the operators and functions form a
self-consistent set. It is the user\'s responsibility to define a valid
operator class.

Related operator classes can be grouped into operator families. To add a
new operator class to an existing family, specify the `FAMILY` option in
`CREATE OPERATOR
   CLASS`. Without this option, the new class is placed into a family
named the same as the new class (creating that family if it doesn\'t
already exist).

Refer to [???](#xindex) for further information.

Parameters
==========

name

:   The name of the operator class to be created. The name can 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.

family\_name

:   The name of the existing operator family to add this operator class
    to. If not specified, a family named the same as the operator class
    is used (creating it, if it doesn\'t already exist).

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 associated
    with the operator class.

op\_type

:   In an `OPERATOR` clause, the operand data type(s) of the operator,
    or `NONE` to signify a prefix operator. The operand data types can
    be omitted in the normal case where they are the same as the
    operator class\'s data type.

    In a `FUNCTION` clause, the operand data type(s) the function is
    intended to support, if different from the input data type(s) of the
    function (for B-tree comparison functions and hash functions) or the
    class\'s data type (for B-tree sort support functions, B-tree equal
    image functions, and all functions in GiST, SP-GiST, GIN and BRIN
    operator classes). These defaults are correct, and so op\_type need
    not be specified in `FUNCTION` clauses, except for the case of a
    B-tree sort support function that is meant to support
    cross-data-type comparisons.

sort\_family\_name

:   The name (optionally schema-qualified) of an existing `btree`
    operator family that describes the sort ordering associated with an
    ordering operator.

    If neither `FOR SEARCH` nor `FOR ORDER BY` is specified,
    `FOR SEARCH` is the default.

support\_number

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

function\_name

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

argument\_type

:   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 (currently
    GiST, GIN, SP-GiST and BRIN) allow it to be different. The `STORAGE`
    clause must be omitted unless the index method allows a different
    type to be used. If the column data\_type is specified as
    `anyarray`, the storage\_type can be declared as `anyelement` to
    indicate that the index entries are members of the element type
    belonging to the actual array type that each particular index is
    created for.

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

Notes
=====

Because the index machinery does not check access permissions on
functions before using them, including a function or operator in an
operator class is tantamount to granting public execute permission on
it. This is usually not an issue for the sorts of functions that are
useful in an operator class.

The operators should not be defined by SQL functions. An SQL function is
likely to be inlined into the calling query, which will prevent the
optimizer from recognizing that the query matches an index.

Before PostgreSQL 8.4, the `OPERATOR` clause could include a `RECHECK`
option. This is no longer supported because whether an index operator is
"lossy" is now determined on-the-fly at run time. This allows efficient
handling of cases where an operator might or might not be lossy.

Examples
========

The following example command defines a GiST index operator class for
the data type `_int4` (array of `int4`). See the [???](#intarray) module
for the complete example.

    CREATE OPERATOR CLASS gist__int_ops
        DEFAULT FOR TYPE _int4 USING gist AS
            OPERATOR        3       &&,
            OPERATOR        6       = (anyarray, anyarray),
            OPERATOR        7       @>,
            OPERATOR        8       <@,
            OPERATOR        20      @@ (_int4, query_int),
            FUNCTION        1       g_int_consistent (internal, _int4, smallint, oid, internal),
            FUNCTION        2       g_int_union (internal, 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
========
