Strategy Specification

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Strategy Specification

The STRATEGIES keyword introduces a comma-separated list of function names or function signatures for the new operator class. Each element of this list is called a strategy specification and has the following syntax:

Strategy Specification:
 
|--strategy_function-------------------------------------------->
 
>--+-----------------------------------------------------+------|
   '-(--input_type--,--input_type--+----------------+--)-'
                                   '-,--output_type-'

Element	Description	Restrictions	Syntax
input_type	Data type of an input parameter to the strategy function for which you intend to use a specific secondary-access method	A strategy function accepts two input parameter and can have one optional output parameter	Data Type
output_type	Data type of the optional output parameter of the strategy function	Optional output parameter for side-effect indexes	Data Type
strategy_function	Strategy function to associate with the specified operator class	Must be listed in the order that the specified secondary-access method expects	Database Database Object Name

Each strategy_function is an external function. The CREATE OPCLASS statement does not verify that a user-defined function of the name you specify exists. However, for the secondary-access method to use the strategy function, the external function must be:

Compiled in a shared library
Registered in the database with the CREATE FUNCTION statement

Optionally, you can specify the signature of a strategy function in addition to its name. A strategy function requires two input parameters and an optional output parameter. To specify the function signature, specify:

An input data type for each of the two input parameters of the strategy function, in the order that the strategy function uses them
Optionally, one output data type for an output parameter of the strategy function

You can specify UDTs as well as built-in data types. If you do not specify the function signature, the database server assumes that each strategy function takes two arguments of the same data type and returns a BOOLEAN value.