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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
Extend data types
This section describes the ways to extend data types with C user-defined routines (UDRs).
Create an Opaque Data Type
This section describes how to design and write an opaque data type.
Write opaque-type support functions
The database server does not know the internal representation of an opaque type. To handle the internal representation, you write opaque-type support functions. These support functions tell the database server how to interact with the opaque type.
Support functions as casts
The input and output support functions
To handle opaque-type data in its external text representation, the database server calls the input and output support functions for the opaque type.
Conversion of opaque-type data between text and binary representations
The input and output support functions can call the following DataBlade® API functions to convert the atomic C data types within the server internal representation of the opaque data type between their external (text) and internal (binary) representations.

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.
      - Extend data types
        This section describes the ways to extend data types with C user-defined routines (UDRs).
        Create an Opaque Data Type
        This section describes how to design and write an opaque data type.
        Design an opaque data type
        Write opaque-type support functions
        The database server does not know the internal representation of an opaque type. To handle the internal representation, you write opaque-type support functions. These support functions tell the database server how to interact with the opaque type.
        Support functions as casts
        The input and output support functions
        To handle opaque-type data in its external text representation, the database server calls the input and output support functions for the opaque type.
        The input support function
        When an application performs some operation that passes the external representation of an opaque type to the database server (such as INSERT or UPDATE with an opaque-type value as a literal string), the database server calls the input support function.
        The output support function
        When an application performs some operation that requests the external representation of an opaque type (such as a SELECT operation that requests data in its text representation), the database server calls the output support function.
        Conversion of opaque-type data between text and binary representations
        The input and output support functions can call the following DataBlade® API functions to convert the atomic C data types within the server internal representation of the opaque data type between their external (text) and internal (binary) representations.
        The send and receive support functions
        To handle opaque-type data in its external binary representation, the database server calls the send and receive support functions for the opaque type.
        Bulk-copy support functions
        The database server can copy data in and out of a database with a bulk copy operation. In a bulk copy, the database server reads or sends large numbers of column values in a copy file, rather than handling each column value individually.
        External unload representation
        To handle opaque-type data in its external unload representation, the database server calls the import and export support functions of the opaque type. The external unload representation is the text version of the opaque-type data when it is in a copy file. Usually, the external unload and external representations of an opaque type are the same.
        Internal unload representation
        To handle opaque-type data in its internal unload representation, the database server calls the importbin and exportbin support functions of the opaque type. The internal unload representation is the binary version of the opaque-type data when it is in a copy file. Usually, the internal unload and server internal representations of an opaque type are the same.
        Stream support functions
        Disk-storage support functions
        Handling locale-specific opaque-type data (GLS)
        Registering an opaque data type
        This section explains how to register an opaque data type.
        Provide statistics data for a column
        The database server can provide statistics data for the columns of a table. This statistics data describes the distribution of the values within a column. The query optimizer uses this statistics data to determine the best path for an SQL statement. With this information, the optimizer can estimate the effect of a WHERE clause by examining, for each column included in the WHERE clause, the proportionate occurrence of data values contained in the column.
        Optimize queries
    - 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.

Conversion of opaque-type data between text and binary representations

The input and output support functions can call the following DataBlade® API functions to convert the atomic C data types within the server internal representation of the opaque data type between their external (text) and internal (binary) representations.

Table 1. Input and output DataBlade® API support functions for date and date/time data
Type of data	The streamwrite() support function	The streamread() support function
DATE data	mi_string_to_date()	mi_date_to_string()
DATETIME data	mi_string_to_datetime()	mi_datetime_to_string()
INTERVAL data	mi_string_to_interval()	mi_interval_to_string()

Table 2. Input and output DataBlade® API support functions for integer data
Type of data	The streamwrite() support function	The streamread() support function
SMALLINT data (two-byte integers)	rstoi(), atoi()
INTEGER data (four-byte integers)	rstol(), atol()
INT8 data (eight-byte integers)	ifx_int8cvasc()	ifx_int8toasc()

Table 3. Input and output DataBlade® API support functions for fixed-point and floating-point data
Type of data	The streamwrite() support function	The streamread() support function
DECIMAL data (fixed-point and floating-point)	mi_string_to_decimal()	mi_decimal_to_string()
MONEY data	mi_string_to_money()	mi_money_to_string()
SMALLFLOAT data	atof()
FLOAT data	rstod()

Table 4. Input and output DataBlade® API support functions for other data
Type of data	The streamwrite() support function	The streamread() support function
Character data, Varying-length data	mi_string_to_lvarchar()	mi_lvarchar_to_string()
LO handle (smart large objects)	mi_lo_from_string()	mi_lo_to_string()

Most DataBlade® API functions that convert between text and binary representations recognize the end-user formats for data in a locale-specific format. For more information about how to internationalize a C UDR, see Internationalization of DataBlade API modules (GLS).