CREATE OPERATOR CLASS() SQL Commands CREATE OPERATOR CLASS()
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 ) ] [ RECHECK ]
| FUNCTION support_number [ ( op_type [ , op_type ] ) ] 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 oper-
ator class specifies that certain operators will fill particular roles
or ``strategies'' for this data type and this index method. The opera-
tor 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 oper-
ator 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 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 op-
erand 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 and hash indexes) or the class's data
type (for GIN and GiST indexes). These defaults are always cor-
rect, so there is no point in specifying op_type in a FUNCTION
clause in CREATE OPERATOR CLASS, but the option is provided for
consistency with the comparable syntax in ALTER OPERATOR FAMILY.
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 asso-
ciated 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 (currently
GIN and GiST) 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 func-
tions before using them, including a function or operator in an opera-
tor 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.
EXAMPLES
The following example command defines a GiST index operator class for
the data type _int4 (array of int4). See contrib/intarray/ for the com-
plete 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);
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(l)], DROP OPERATOR CLASS
[drop_operator_class(l)], CREATE OPERATOR FAMILY [create_operator_fam-
ily(l)], ALTER OPERATOR FAMILY [alter_operator_family(l)]
SQL - Language Statements 2008-09-19 CREATE OPERATOR CLASS()
postgresql 8.3.4 - Generated Thu Oct 2 11:42:30 CDT 2008