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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 extensions
You 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 Guide
The 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 UDRs
This section describes how to create special UDRs, such as iterator functions, user-defined aggregates, and optimization functions.
Provide UDR-optimization functions
implementing a negator function with a C user-defined function
A negator function is a special UDR that is associated with a Boolean user-defined function. It evaluates the Boolean NOT condition for its associated user-defined function.

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.
- Informix® extensions and DataBlade® modules
  These topics describe how to use built-in database extensions and separately installed DataBlade® modules.
- Creating extensions
  You 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 Guide
    The Informix® DataBlade® API Programmer's Guide describes information about the DataBlade API, the C-language application programming interface (API) provided with HCL Informix.
    - DataBlade® API overview
    - Data manipulation
    - Database access
    - Create user-defined routines
      - Develop a user-defined routine
        A C user-defined routine (UDR) is a UDR that is written in the C language and uses the server-side implementation of the DataBlade® API to communicate with the database server. C UDRs (functions and procedures) are implemented as C-language functions. DataBlade modules often include C UDRs that are made available for use by registering them in the database.
      - Write a user-defined routine
        This section outlines some implementation issues for C user-defined routines (UDRs). This section also describes the specific features and tasks of a C UDR.
      - Manage memory
        A C user-defined routine (UDR) has access to shared memory for dynamic allocations and stack memory for routine arguments (including the MI_FPARAM structure), local stack variables, and return values.
      - Create special-purpose UDRs
        This section describes how to create special UDRs, such as iterator functions, user-defined aggregates, and optimization functions.
        Write an end-user routine
        A C UDR can implement an end-user routine. An end-user routine provides some additional functionality to the SQL end user. It is an SQL-invoked routine; that is, it is called directly from an SQL statement. An end-user routine can provide any task that is useful to SQL users. This user might be a database administrator or an SQL end user.
        Write a cast function
        A cast function is a user-defined function that converts one data type (the source data type), to another data type (the target data type).
        Write an iterator function
        An iterator function is a user-defined function that returns to its calling SQL statement several times, each time returning a value.
        Write an aggregate function
        An aggregate is a function that returns one value for a group of queried rows. The aggregate function performs one iteration for each of the queried rows.
        Provide UDR-optimization functions
        Write selectivity and cost functions
        The query optimizer uses the selectivity and cost of a query to help select the best query plan. To help the optimizer select the best query plan, you can provide the query optimizer with information about the selectivity and cost of your UDR.
        implementing a negator function with a C user-defined function
        A negator function is a special UDR that is associated with a Boolean user-defined function. It evaluates the Boolean NOT condition for its associated user-defined function.
        Implementing a commutator function with a C user-defined function
        A commutator function is a special UDR that is associated with a user-defined function.
        Creating parallelizable UDRs
        A parallelizable query is a query that can be executed in parallel.
      - Extend data types
        This section describes the ways to extend data types with C user-defined routines (UDRs).
    - Appendix
      This section contains additional reference information.
  - DataBlade® API Function Reference
    The Informix® DataBlade® API Function Reference describes the DataBlade API functions and the subset of Informix ESQL/C functions that the DataBlade API supports.
  - DataBlade® Developers Kit
    The 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 Informix® databases.
  - J/Foundation Developer's Guide
    The J/Foundation Developer's Guide describes how to write user-defined routines (UDRs) in the Java™ programming language for Informix®.
  - R-Tree Index User's Guide
    The Informix® R-Tree Index User's Guide describes the HCL Informix R-tree secondary access method and how to access and use its components.
  - User-Defined Routines and Data Types Developer's Guide
    The Informix® User-Defined Routines and Data Types Developer's Guide describes how to define new data types and enable user-defined routines (UDRs) to extend HCL Informix.
  - Virtual-Table Interface Guide
    The 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.
  - Virtual-Index Interface Guide
    The Informix® Virtual-Index Interface Programmer's Guide explains how to create a secondary access method with the Virtual-Index Interface (VII) to extend the built-in indexing schemes of HCL Informix typically with a DataBlade® module.

implementing a negator function with a C user-defined function

A negator function is a special UDR that is associated with a Boolean user-defined function. It evaluates the Boolean NOT condition for its associated user-defined function.

About this task

For example, if an expression in a WHERE clause invokes a Boolean user-defined function (UDR-Boolfunc), the SQL optimizer can decide whether it is more efficient to replace occurrences of the expression

NOT (UDR-Boolfunc)

with a call to the negator function (UDR-func-negator).

To implement a negator function with a C user-defined function:

Procedure

Declare the negator function so that its parameters are exactly the same as its associated user-defined function and its return value is BOOLEAN (mi_boolean).
Within the negator function, perform the tasks to evaluate the NOT condition of the associated Boolean user-defined function.
Register the negator function as a user-defined function with the CREATE FUNCTION statement.
Associate the Boolean user-defined function and its negator function when you register the user-defined function.
Specify the name of the negator function with the NEGATOR routine modifier in the CREATE FUNCTION statement that registers the user-defined function.

Results

For more information about Boolean user-defined functions and negator functions, see the Informix® User-Defined Routines and Data Types Developer's Guide. For information about how to determine if a user-defined function has a negator function, see Determine if a function is a negator function.