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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
Develop a user-defined routineA C user-defined routine (UDR) is a UDR that is written in the C language and uses the server-side implementation of the DataBlade® API to communicate with the database server. C UDRs (functions and procedures) are implemented as C-language functions. DataBlade® modules often include C UDRs that are made available for use by registering them in the database.
Creating UDR codeThis section provides an overview of C UDR development.
SQL statement executionThe differences in the execution of SQL statements in a C UDR and a client LIBMI application are because of the differences in passing mechanisms that they use for the contents of an MI_DATUM structure. In a C UDR, you must consider the data type of the value in the MI_DATUM structure to determine how to obtain the value.
Set input parameters

Set input parameters

When you send a prepared statement for execution, you pass any input-parameter values in MI_DATUM structures. Therefore, the data type of the column associated with an input parameter determines the passing mechanism for the input-parameter value, as follows:

For data types that are passed by value, the MI_DATUM structure must contain the actual input-parameter value.
For data types that are passed by reference, the MI_DATUM structure must contain a pointer to the input-parameter value.

Within your C UDR, you must use the column data type to determine how to assign the input-parameter value in the MI_DATUM structure. To assign the input-parameter values, you send an array of MI_DATUM structures to the mi_exec_prepared_statement() or mi_open_prepared_statement() function, which sends the prepared statement to the database server for execution. For more information, see Assign values to input parameters.

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