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Extending Informix®Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix® includes many built-in extensions that are fully integrated in the database server. Informix® also provides DataBlade® modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix®.
Creating extensionsYou can create user-defined data types, routines, access methods, and other database objects to suit your needs. You can use application programming interfaces to write user-defined routines and applications that access data in Informix® databases.
DataBlade® API Programmer's GuideThe Informix® DataBlade® API Programmer's Guide describes information about the DataBlade® API, the C-language application programming interface (API) provided with HCL Informix®.
Create user-defined routines
Create special-purpose UDRsThis section describes how to create special UDRs, such as iterator functions, user-defined aggregates, and optimization functions.
Provide UDR-optimization functions
implementing a negator function with a C user-defined functionA negator function is a special UDR that is associated with a Boolean user-defined function. It evaluates the Boolean NOT condition for its associated user-defined function.

implementing a negator function with a C user-defined function

A negator function is a special UDR that is associated with a Boolean user-defined function. It evaluates the Boolean NOT condition for its associated user-defined function.

About this task

For example, if an expression in a WHERE clause invokes a Boolean user-defined function (UDR-Boolfunc), the SQL optimizer can decide whether it is more efficient to replace occurrences of the expression

NOT (UDR-Boolfunc)

with a call to the negator function (UDR-func-negator).

To implement a negator function with a C user-defined function:

Procedure

Declare the negator function so that its parameters are exactly the same as its associated user-defined function and its return value is BOOLEAN (mi_boolean).
Within the negator function, perform the tasks to evaluate the NOT condition of the associated Boolean user-defined function.
Register the negator function as a user-defined function with the CREATE FUNCTION statement.
Associate the Boolean user-defined function and its negator function when you register the user-defined function.
Specify the name of the negator function with the NEGATOR routine modifier in the CREATE FUNCTION statement that registers the user-defined function.

Results

For more information about Boolean user-defined functions and negator functions, see the Informix® User-Defined Routines and Data Types Developer's Guide. For information about how to determine if a user-defined function has a negator function, see Determine if a function is a negator function.

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