Defines a new operator class.
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> <funcname> (<argument_type> [, ...] )
| STORAGE <storage_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 is created. Any functions used to implement the operator class must be defined as IMMUTABLE
.
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.
You must be a superuser to create an operator class.
btree
,
bitmap
, and
gist
.
Operation | Strategy Number |
---|---|
less than | 1 |
less than or equal | 2 |
equal | 3 |
greater than or equal | 4 |
greater than | 5 |
Operation | Strategy Number |
---|---|
strictly left of | 1 |
does not extend to right of | 2 |
overlaps | 3 |
does not extend to left of | 4 |
strictly right of | 5 |
same | 6 |
contains | 7 |
contained by | 8 |
does not extend above | 9 |
strictly below | 10 |
strictly above | 11 |
does not extend below | 12 |
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.
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.
Function | Support Number |
---|---|
Compare two keys and return an integer less than zero, zero, or greater than zero, indicating whether the first key is less than, equal to, or greater than the second. | 1 |
Function | Support Number |
---|---|
consistent - determine whether key satisfies the query qualifier. | 1 |
union - compute union of a set of keys. | 2 |
compress - compute a compressed representation of a key or value to be indexed. | 3 |
decompress - compute a decompressed representation of a compressed key. | 4 |
penalty - compute penalty for inserting new key into subtree with given subtree’s key. | 5 |
picksplit - determine which entries of a page are to be moved to the new page and compute the union keys for resulting pages. | 6 |
equal - compare two keys and return true if they are equal. | 7 |
STORAGE
clause must be omitted unless the index method allows a different type to be used.
Because the index machinery does not check access permissions on functions before using them, including a function or operator in an operator class is the same as 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.
Any functions used to implement the operator class must be defined as IMMUTABLE
.
Before Greenplum Database 6.0, the OPERATOR
clause could include a RECHECK
option. This option is no longer supported. Greenplum Database now determines whether an index operator is “lossy” on-the-fly at run time. This allows more 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
contrib 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);
CREATE OPERATOR CLASS
is a Greenplum Database extension. There is no CREATE OPERATOR CLASS
statement in the SQL standard.
ALTER OPERATOR CLASS, DROP OPERATOR CLASS, CREATE FUNCTION
Parent topic: SQL Commands