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CREATE OPERATOR CLASS(7) PostgreSQL 9.2.24 Documentation CREATE OPERATOR CLASS(7)
NAME
CREATE_OPERATOR_CLASS - define a new operator class
SYNOPSIS
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 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 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 Section 35.14, "Interfacing Extensions To Indexes", in the documentation 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
left-unary or right-unary 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 and
all functions in GiST, SP-GiST and GIN 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 procedure 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
procedure 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 and GIN) 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 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. 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.
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, int, 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
ALTER OPERATOR CLASS (ALTER_OPERATOR_CLASS(7)), DROP OPERATOR CLASS
(DROP_OPERATOR_CLASS(7)), CREATE OPERATOR FAMILY (CREATE_OPERATOR_FAMILY(7)), ALTER
OPERATOR FAMILY (ALTER_OPERATOR_FAMILY(7))
PostgreSQL 9.2.24 2017-11-06 CREATE OPERATOR CLASS(7)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
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