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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.
Virtual-Index Interface GuideThe 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.
Descriptor function reference
Accessor functionsThe Virtual-Index Interface (VII) library contains functions that primarily access selected fields from the various descriptors.
The mi_scan_projs() accessor functionThe mi_scan_projs() function identifies each key column.

The mi_scan_projs() accessor function

The mi_scan_projs() function identifies each key column.

Syntax

mi_smallint * mi_scan_projs(MI_AM_SCAN_DESC *scanDesc)

Use the return value from mi_scan_nprojs() to determine the number of times to execute mi_scan_projs().

Each of the small integers in the array that this function returns identifies a column by the position of that column in the row descriptor.