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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
Write a user-defined routineThis section outlines some implementation issues for C user-defined routines (UDRs). This section also describes the specific features and tasks of a C UDR.
Code a C UDRWhen you code a C UDR, you define routine parameters, obtain argument values, define a return value, and code the routine body to write a C function.
Obtain argument valuesTo obtain the argument value with a C UDR, access the parameter that you have specified in the C declaration of the function. The parameter declaration indicates the appropriate passing mechanism for the UDR parameters.
Modify argument values

Modify argument values

Do not modify a UDR argument unless it is an OUT parameter. The routine manager does not make routine-specific copies of the arguments that it passes to UDRs because it is more efficient not to do so. Keep in mind that values passed into a UDR are often used on other places in the SQL statement. If you modify a pass-by-reference value within the UDR, you also modify it for all other parts of the SQL statement (including other UDRs) that operate on the value after the UDR executes. When you modify a pass-by-reference argument within the UDR, you might create an order-dependent result of the SQL statement. That is, it now might make a difference when your UDR is run within the SQL statement.

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