CREATE OPERATOR CLASS — define a new operator class
CREATE OPERATOR CLASSname
[ DEFAULT ] FOR TYPEdata_type
USINGindex_method
[ FAMILYfamily_name
] AS { OPERATORstrategy_number
operator_name
[ (op_type
,op_type
) ] [ FOR SEARCH | FOR ORDER BYsort_family_name
] | FUNCTIONsupport_number
[ (op_type
[ ,op_type
] ) ]function_name
(argument_type
[, ...] ) | STORAGEstorage_type
} [, ... ]
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 37.14 for further information.
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, 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 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, GIN 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.
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.
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);
CREATE OPERATOR CLASS
is a
PostgreSQL extension. There is no
CREATE OPERATOR CLASS
statement in the SQL
standard.