Проект OpenNet: MAN create_operator_class (7) Макропакеты и соглашения (FreeBSD и Linux)

Интерактивная система просмотра системных руководств (man-ов)

create_operator_class (7)

>> create_operator_class (7) ( Разные man: Макропакеты и соглашения )

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 the documentation 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 associated 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 different type to be used.

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

NOTES

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

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);