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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-Table Interface GuideThe 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®.
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.

This flowchart shows am_scancost pointing to am_open, which points to am_beginscan, which points to am_getnext, which either returns MI_ROWS and re-executes, or returns MI_NO_MORE_RESULTS. — Figure 1: Processing a SELECT statement scan

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