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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.
Purpose-function referenceThese topics describe the purpose functions that the access-method developer provides.
Purpose-function flowThe diagrams in this section show, for each SQL statement, which purpose functions the database server executes. Use the diagrams to determine which purpose functions to implement in the access method.
The SELECT...WHERE statement interface

The SELECT...WHERE statement interface

The following figure shows the order in which the database server executes purpose functions for a SELECT statement with a WHERE clause.

Flowchart shows am_scancost pointing to am_open, which points to am_beginscan, which points to am_getnext. If the am_getnext returns MI_ROWS, the scan executes am_getnext again. If am_getnext returns MI_NO_MORE_RESULTS, the scan continues to am_endscan, which points to am_close. — Figure 1: Processing a SELECT statement scan

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