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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.
The R-tree secondary access method
Perform nearest-neighbor searches
Limitations

Limitations

The WHERE clause of a nearest-neighbor query cannot include:

Clauses connected by OR
Clauses connected by AND NOT

Only one nearest-neighbor function can be used per query.

Using a fragmented R-tree index for nearest-neighbor queries raises an error. The results are not returned in nearest-distance order because the query is executed on each separate index fragment, and results from each fragment are combined in an unspecified order.

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