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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
When does the query optimizer use an R-tree index?
Complex qualifications

Complex qualifications

A complex qualification is a WHERE clause in which two or more logical operators are used on the same column on which the R-tree index is defined.

If you specify a complex qualification in a query that includes only AND or only OR logical operators, then the entire qualification is evaluated using one R-tree index scan. An example of a complex qualification that uses only AND logical operators is WHERE Overlap(A,B) AND Contains(A,C) AND Contains(A,D), where A is the indexed column. An example of a complex qualification that uses only OR logical operators is WHERE Overlap(A,B) OR Contains(A,C) OR Contains(A,D).

If, however, you mix AND and OR logical operators in the same complex qualification, the R-tree index is not used at all for any of the predicates. This means that arbitrary logical expressions cannot necessarily use an R-tree index. An example of a complex qualification that mixes AND and OR logical operators is WHERE Overlap(A,B) AND Contains(A,C) OR Contains(A,D), where A is the indexed column.

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