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Extending HCL OneDB™Beyond standard relational database objects, HCL OneDB™ can be extended to handle specialized data types, access methods, routines, and other objects. HCL OneDB™ includes many built-in extensions that are fully integrated in the database server. HCL OneDB™ 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 HCL OneDB™.
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 HCL OneDB™ databases.
DataBlade® Developers KitThe DataBlade® Developers Kit (DBDK) guides contain information about the tools you can use to develop and package DataBlade® modules, which extend the functionality of HCL OneDB™ databases.
DataBlade® Developers Kit User's GuideThe HCL OneDB™ DataBlade® Developers Kit Users Guide describes how to use OneDB® DataBlade® Developers Kit (DBDK) tools to develop and package DataBlade® modules.
Design DataBlade® modulesThis section describes the DataBlade® module SQL design issues.
Query processingTo develop a DataBlade® module, you need a general understanding of query processing and HCL OneDB™ SQL. You must also understand the execution environment inside your HCL OneDB™ database server ̵ the multithreading model, the collection of processes in which DataBlade® module routines can execute, and concurrent access to database objects, transactions, and so on.
Access path selectionDuring query processing, your database server takes a nonprocedural query and produces a procedural plan for satisfying it; this process is called making an access path selection.

Access path selection

During query processing, your database server takes a nonprocedural query and produces a procedural plan for satisfying it; this process is called making an access path selection.

Queries are nonprocedural because they describe only the records of interest and what operations to perform on them. They do not prescribe an algorithm (procedure) for locating records on disk or the order in which to process them.

Your database server evaluates a collection of possible query plans that can execute the query correctly. The server estimates the cost of running each plan and chooses the one with the smallest cost estimate. Cost estimates are a combination of the number of expected disk I/Os, the expected number of records that must be processed, and the cost of invoking each of the routines in the query on each candidate row.