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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.
R-Tree Index User's GuideThe 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
Creating a new operator class
Support functions
The Size function

The Size function

The R-tree access method uses the Size function to evaluate different ways to group objects by comparing the sizes of bounding boxes around objects or groups of objects. It does this when it decides where to place a new data object and when it splits a page. Ideally, a disk page is divided into two pages whose overall bounding boxes are as compact and small as possible.

For sample C code of the Size function, see Size support function. C code uses the DataBlade® API to interact with the database server.

The SQL signature of the Size support function must be:

Size (UDT, DOUBLE PRECISION) RETURNS INTEGER

UDT refers to user-defined type, or the data type you want to index with the R-tree access method.

Write the Size function to calculate the relative size of the bounding box of the object in the first parameter and to store the result in the second parameter as a double-precision value.

The return value of the Size function is not used by the R-tree access method. The Size function should call the mi_db_error_raise() DataBlade API function to return errors.

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