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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® Developers KitThe DataBlade® Developers Kit (DBDK) guides contain information about the tools you can use to develop and package DataBlade® modules, which extend the functionality of HCL Informix® databases.
DataBlade® Developers Kit User's GuideThe HCL Informix® DataBlade® Developers Kit User's Guide describes how to use tools to develop and package DataBlade® modules.
Design DataBlade® modulesThis section describes the DataBlade® module SQL design issues.
Query processingTo develop a DataBlade® module, you need a general understanding of query processing and HCL Informix® SQL. You must also understand the execution environment inside your Informix® database server ̵ the multithreading model, the collection of processes in which DataBlade® module routines can execute, and concurrent access to database objects, transactions, and so on.
Access path selectionDuring query processing, your database server takes a nonprocedural query and produces a procedural plan for satisfying it; this process is called making an access path selection.
Unordered row processing

Unordered row processing

When you design a DataBlade® module, you cannot control how queries are executed. There is no guarantee that the routines in a query are called in any particular order. DataBlade module routines are called during query processing to compute answers to queries. Do not hardcode query execution strategies. For example, an attempt to force an index scan or a sequential table scan reduces the number of choices available to the query optimizer and results in poor performance.

To ensure that your DataBlade module does not conflict with the query processing engine, ask the following questions:

Do any routines require values to be delivered in some particular order? If so, the routines break a fundamental rule of relational database systems and must be changed.
Is it important for routines in a query to execute in some particular sequence? Again, the routines must be changed.

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