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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.
DataBlade® API Programmer's GuideThe Informix® DataBlade® API Programmer's Guide describes information about the DataBlade® API, the C-language application programming interface (API) provided with HCL Informix®.
Create user-defined routines
Create special-purpose UDRsThis section describes how to create special UDRs, such as iterator functions, user-defined aggregates, and optimization functions.
Provide UDR-optimization functions
Creating parallelizable UDRsA parallelizable query is a query that can be executed in parallel.

Creating parallelizable UDRs

A parallelizable query is a query that can be executed in parallel.

About this task

The Parallel Database Query (PDQ) feature allows the database server to run a single SQL statement in parallel. When you send a query to the database server, it breaks your request into a set of discrete subqueries, each of which can be assigned to a different CPU virtual processor. PDQ is especially effective when your tables are fragmented and your server computer has more than one CPU.

A parallelizable UDR is a C UDR that can be executed in parallel when it is invoked within a parallelizable query. If you write your C UDR to be parallelizable, it can be executed in parallel when the query that invokes it is executed in parallel. That is, the C UDR can execute on subsets of table data just as the query itself can. A query that invokes a nonparallelizable UDR can still run in parallel. However, the calls to the UDR do not run in parallel. Similarly, prepared queries that invoke a parallelizable query do not run the UDR in parallel.

To create a parallelizable C UDR:

Procedure

Write the C UDR so that it does not call any DataBlade® API functions that are non-PDQ-threadsafe.
Register the C UDR with the PARALLELIZABLE routine modifier.
Execute the parallelized C UDR, once in each scan thread of the parallelized query.
Debug the parallelized C UDR.

Results

The following subsections describe these steps in detail.

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