Welcome
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 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.
Programmer's Guide
The HCL® Informix® DataBlade® API Programmer's Guide describes information about the , 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
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.
Obtain information about constant arguments

HCL Informix® V15.0.0 documentation
Welcome to the documentation for HCL Informix® 15.0.0 and related client tools and products.
Product overview
HCL Informix® is a fast and scalable database server that manages traditional relational, object-relational, and dimensional databases. Its small footprint and self-managing capabilities are suited to embedded data-management solutions.
Installing
These topics describe how to install HCL Informix® database servers, client products, and modules.
Administering
In addition to administering the database server, you can tune performance, replicate data, and archive data.
Migrating and upgrading
You can upgrade to the 15.0.0 release of HCL Informix® or migrate from other database servers to Informix. Upgrading is an in-place migration method that uses your existing hardware and operating system software. Some changes to the Informix database server can affect upgrading from a previous release.
Client APIs and tools
You can use the HCL Informix® implementation of client APIs to develop applications for Informix database servers.
Embedding Informix®
When you embed HCL Informix®, you can use enterprise-class high-availability and high performance with embeddability features such as easy programmability, a small disk and memory footprint, and silent deployment.
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 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 modules
  These topics describe how to use built-in database extensions and separately installed 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.
  - Programmer's Guide
    The HCL® Informix® DataBlade® API Programmer's Guide describes information about the , the C-language application programming interface (API) provided with HCL Informix.
    - 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 to communicate with the database server. C UDRs (functions and procedures) are implemented as C-language functions. 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.
        Query selectivity
        If your UDR is a Boolean function, it can be used as a filter in a query. The query optimizer uses the selectivity of a query to estimate the number of rows that the query will return. The selectivity is a floating-point value between zero and one that represents the percentage of rows for which the query (and each filter in the query) is expected to return a true value.
        Query cost
        If your UDR requires a lot of system resources (such as a large number of disk accesses or network accesses), you can define a cost-of-execution for the UDR. The query optimizer uses the cost value to determine the total cost of executing a query.
        The MI_FUNCARG data type
        The MI_FUNCARG data type is an opaque type defined for HCL Informix® that contains information about the companion UDR of a selectivity or cost function.
        Obtain information about constant arguments
        Obtain information about column arguments
        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.
  - Function Reference
    The IBM® Informix® DataBlade® API Function Reference describes the functions and the subset of functions that the supports.
  - Developers Kit
    The Developers Kit (DBDK) guides contain information about the tools you can use to develop and package modules, which extend the functionality of HCL Informix® databases.
  - J/Foundation Developer's Guide
    The HCL® 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 HCL® 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 HCL® 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 IBM® 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 IBM® 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 module.
Data warehousing
In addition to designing and implementing Informix® dimensional databases, you can use tools to create data warehouse applications and optimize your data warehouse queries.
Designing databases
The first step in creating a relational database is to construct a data model, which is a precise, complete definition of the data you want to store. After you prepare your data model, you must implement it as a database and tables. To implement your data model, you first select a data type for each column and then you create a database and tables and populate the tables with data. You can also implement fragmentation strategies and control access to your data.
JSON compatibility
You can use the popular JSON-oriented query language created by MongoDB to interact with data stored in HCL Informix®.
Security
You can secure your Informix® database server and the data that is stored in your Informix databases. You can encrypt data, secure connections, control user privileges and access, and audit data security.
SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
Troubleshooting HCL Informix®
Several troubleshooting techniques, tools, and resources are available for resolving problems that you encounter in your HCL Informix® database server environment.

Obtain information about constant arguments

When the companion UDR receives an argument that is a constant, you can obtain the following information about this constant from within the cost or selectivity function.


MI_FUNCARG information	function
The constant value of the companion-UDR argument	mi_funcarg_get_constant()
Determines if the value of the companion-UDR argument is the SQL NULL value	mi_funcarg_isnull()