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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®.
Descriptor function referenceThese topics provide the syntax and usage for the functions that the HCL Informix® database server supplies to access-method developers.
Accessor functionsThe Virtual-Table Interface (VTI) library contains functions that primarily access selected fields from the various descriptors.
The mi_qual_const_depends_outer() accessor functionThe mi_qual_const_depends_outer() function indicates that an outer join provides the constant in a qualification.

The mi_qual_const_depends_outer() accessor function

The mi_qual_const_depends_outer() function indicates that an outer join provides the constant in a qualification.

Syntax

mi_boolean
mi_qual_const_depends_outer(MI_AM_QUAL_DESC *qualDesc)

qualDesc: Points to the qualification descriptor.

Usage

If this mi_qual_const_depends_outer() evaluates to MI_TRUE, the join or subquery can produce a different constant value for each rescan.

Call mi_qual_const_depends_outer() in am_rescan. If your access method has no am_rescan purpose function, call mi_qual_const_depends_outer() in am_beginscan.

Return values

MI_TRUE: Indicates that the constant depends on an outer join.
MI_FALSE: Indicates that the constant remains the same on a rescan.

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