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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 extensions
You 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.
R-Tree Index User's Guide
The Informix® R-Tree Index User's Guide describes the HCL Informix R-tree secondary access method and how to access and use its components.
Develop DataBlade® modules that use the R-tree secondary access method
Design a user-defined data type
Implementing data type hierarchy

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.
- Informix® extensions and DataBlade® modules
  These topics describe how to use built-in database extensions and separately installed DataBlade® modules.
- Creating extensions
  You 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 Guide
    The Informix® DataBlade® API Programmer's Guide describes information about the DataBlade API, the C-language application programming interface (API) provided with HCL Informix.
  - DataBlade® API Function Reference
    The Informix® DataBlade® API Function Reference describes the DataBlade API functions and the subset of Informix ESQL/C functions that the DataBlade API supports.
  - DataBlade® Developers Kit
    The 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.
  - J/Foundation Developer's Guide
    The J/Foundation Developer's Guide describes how to write user-defined routines (UDRs) in the Java™ programming language for Informix®.
  - R-Tree Index User's Guide
    The Informix® R-Tree Index User's Guide describes the HCL Informix R-tree secondary access method and how to access and use its components.
  - User-Defined Routines and Data Types Developer's Guide
    The Informix® User-Defined Routines and Data Types Developer's Guide describes how to define new data types and enable user-defined routines (UDRs) to extend HCL Informix.
  - Virtual-Table Interface Guide
    The Informix® Virtual-Table Interface Programmer's Guide explains how to create a primary access method with the Virtual-Table Interface (VTI) so that users have a single SQL interface to HCL Informix tables and to data that does not conform to the storage scheme of HCL Informix.
  - Virtual-Index Interface Guide
    The Informix® Virtual-Index Interface Programmer's Guide explains how to create a secondary access method with the Virtual-Index Interface (VII) to extend the built-in indexing schemes of HCL Informix typically with a DataBlade® module.

Implementing data type hierarchy

About this task

If you are designing two or more similar data types, you should consider implementing your own data type hierarchy to avoid writing strategy and support functions for every possible combination of data type signatures.

To implement your own data type hierarchy:

Procedure

Design a single supertype to which the strategy functions apply.
Create implicit casts in SQL from all the subtypes to the supertype.
Create implicit casts in SQL from the built-in data types LVARCHAR, SENDRECV, IMPEXP, and IMPEXPBIN to the supertype and all subtypes.
This is part of the normal opaque user-defined data type creation. For more information about how to create these implicit casts, refer to Informix® User-Defined Routines and Data Types Developer's Guide.
Create the required strategy functions in SQL for just the supertype.
You do not need to create strategy functions for the subtypes because casts from the subtype to the supertype exist.
In SQL, create support functions for the supertype and all the subtypes.
All of these SQL functions, however, can usually be mapped to the same C code; thus only one C function needs to be written.

Results

If the query optimizer is unable to find a function for a particular subtype when it is executing a query, the query optimizer implicitly casts the subtype to the supertype and uses the function defined for the supertype.

The support or strategy function that is defined for the supertype must internally determine what actual data type it is operating on, and then it must execute the code that applies for that particular data type. This means that the internal C code for a function defined for the supertype also contains the C code that applies to all subtypes.