CREATE OPERATOR CLASS

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 the operators that serve particular roles or "strategies" for the data type and index method. The operator class also specifies the support functions that the index method will use when the operator class is selected for an index column. All operators and functions used by the operator class must be defined before the operator class is created.

If a schema name is given, the operator class will be created in the specified schema. Otherwise, it will be created in the current schema. Two operator classes in the same schema can only have the same name if they are used for different index methods.

The user who defines the operator class becomes its owner. Currently, the creating user must be a superuser (this restriction exists because an incorrect operator class definition can confuse or even crash the server).

CREATE OPERATOR CLASS does not currently check whether the operator class definition includes all the operators and functions required by the index method, nor does it check whether the operators and functions form a 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 will be placed in a family of the same name (creating the family if it does not already exist).

Parameters

name

The name of the operator class to be created. The name can be schema-qualified.

DEFAULT

If present, this operator class will be the default operator class for its data type. At most one default operator class can exist 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 that this operator class is for.

family_name

The name of an existing operator family to add this operator class to. If not specified, a family of the same name will be used (creating it if it does not already exist).

strategy_number

The index method strategy number for an operator associated with the operator class.

operator_name

The name of an operator associated with the operator class (can be schema-qualified).

op_type

In an OPERATOR clause, this represents the operand data type(s) of the operator, or NONE to represent a left-unary or right-unary operator. In the common case where the operand data type is the same as the operator's data type, the operand data type(s) can be omitted.

In a FUNCTION clause, this represents the data type(s) that the function supports, if different from the function's input data type (for B-tree comparison functions and hash functions) or the operator class's data type (for B-tree sort support functions and image functions identical to B-tree, as well as all functions in GiST, SP-GiST, GIN, and BRIN operator classes). These defaults are correct, so op_type does not need to be specified in the FUNCTION clause. For B-tree sort support functions, this indicates cross-data-type comparison.

sort_family_name

The name of an existing btree operator family (can be schema-qualified) that describes the sort order associated with a sort operator.

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

support_number

The index method support function number for a function associated with the operator class.

function_name

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

argument_type

The argument data type(s) of the function.

storage_type

The data type actually stored in the index. Usually this is the same as the column data type, but some index methods (currently GiST, GIN, and BRIN) allow them to differ. Unless the index method allows the use of a different type, the STORAGE clause must be omitted. If the data_type column is specified as anyarray, storage_type can be declared as anyelement to indicate that index entries are members of the element type of the actual array type created for each specific index.

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

Notes

Because the index mechanism does not check permissions on functions before using them, including a function or operator in an operator class is equivalent to granting public execute permission on it. This is typically not a problem for functions that are useful in operator classes.

Operators should not be defined with SQL functions. SQL functions are likely to be inlined into the calling query, which prevents the optimizer from recognizing that the query matches an index.

Examples

The following example defines a GiST index operator class for the data type _int4 (int4 array). 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);

See Also

ALTER OPERATOR CLASS, DROP OPERATOR CLASS, CREATE OPERATOR FAMILY, ALTER OPERATOR FAMILY