Home
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.
Database access
Execute SQL statements
One basic task of a DataBlade® API module is to send SQL statements to the database server for execution.
Execute SQL statements
To execute an SQL statement, a DataBlade® API module must send the SQL statement to the database server, where the statement is executed.
Execute prepared SQL statements
A prepared statement is an SQL statement that is parsed and ready for execution. For these statements, you prepare the statement once and execute it as many times as needed.
Send the prepared statement
Assign values to input parameters
Parameter-value length array
The parameter-value length array, lengths, is the sixth argument of the mi_exec_prepared_statement() and mi_open_prepared_statement() functions. Each element of the parameter-value length array is the integer length (in bytes) of the data type for the input-parameter value.

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
      - Connection handling
        This section describes how to initialize, establish, and close connections.
      - Execute SQL statements
        One basic task of a DataBlade® API module is to send SQL statements to the database server for execution.
        Execute SQL statements
        To execute an SQL statement, a DataBlade® API module must send the SQL statement to the database server, where the statement is executed.
        Choose a DataBlade® API function
        Execute basic SQL statements
        The mi_exec() function provides the simplest way to send a basic SQL statement to the database server for execution. A basic SQL statement is one that does not need to be prepared. That is, the statement does not execute many times in the DataBlade® API module or it does not contain input parameters.
        Execute prepared SQL statements
        A prepared statement is an SQL statement that is parsed and ready for execution. For these statements, you prepare the statement once and execute it as many times as needed.
        Prepare an SQL statement
        To turn a statement string for an SQL statement into a format that the database server can execute, use the mi_prepare() statement.
        Obtain input-parameter information
        From a statement descriptor, you can obtain information about an input parameter once an SQL statement has been prepared. An input parameter indicates a value that is provided when the prepared statement executes.
        Send the prepared statement
        Statements with mi_exec_prepared_statement()
        The mi_exec_prepared_statement() function is for the execution of prepared statements, both queries and other valid SQL statements.
        Statements with mi_open_prepared_statement()
        The mi_open_prepared_statement() function is for the execution of queries.
        Assign values to input parameters
        Parameter-value array
        The parameter-value array, values, is the fifth argument of the mi_exec_prepared_statement() and mi_open_prepared_statement() functions. Each element of the parameter-value array is a pointer to an MI_DATUM structure that holds the value for each input parameter.
        Parameter-value length array
        The parameter-value length array, lengths, is the sixth argument of the mi_exec_prepared_statement() and mi_open_prepared_statement() functions. Each element of the parameter-value length array is the integer length (in bytes) of the data type for the input-parameter value.
        Parameter-value null array
        The parameter-value null array, nulls, is the seventh argument of the mi_exec_prepared_statement() and mi_open_prepared_statement() functions.
        Parameter-value type array
        The parameter-value type array, types, is the eighth argument of the mi_exec_prepared_statement() and mi_open_prepared_statement() functions.
        Determine control mode for query data
        The mi_exec_prepared_statement() and mi_open_prepared_statement() functions specify the control mode for the data of a prepared query in their bit-mask control argument.
        Release prepared-statement resources
        When your DataBlade® API module no longer needs a prepared statement, you can release the resources that it uses with the mi_close_statement() function (explicit cursor) or the mi_drop_prepared_statement() function (statement descriptor, including any cursor).
        Execute multiple SQL statements
        A DataBlade® API statement-execution function can send more than one SQL statement to the database server at a time. In this case, the statement string contains several SQL statements, each terminated by a semicolon (;). When the statement string contains more than one SQL statement, the mi_get_result() function executes for each statement in the string.
        Process statement results
        Retrieving query data
        Complete execution
        The DataBlade® API provides functions to complete execution of the current statement.
        Inserting data into the database
        To insert a row of data into a database, you must execute the INSERT statement.
        Save sets
        Save sets provide a mechanism for a DataBlade® API module to access several rows simultaneously.
      - Execute user-defined routines
        This section provides information about how to call a user-defined routine (UDR).
      - Exceptions and events
        This section describes exceptions and events, and explains how to handle them in DataBlade® API modules.
      - XA-compliant external data sources
    - Create user-defined routines
    - 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.

Parameter-value length array

The parameter-value length array, lengths, is the sixth argument of the mi_exec_prepared_statement() and mi_open_prepared_statement() functions. Each element of the parameter-value length array is the integer length (in bytes) of the data type for the input-parameter value.

The meaning of the values in the lengths array depends on the control mode of the input-parameter values, as follows:

For input-parameter values that are in text representation, the lengths array lists the lengths of the text strings.
Make sure the lengths value matches the length of the null-terminated string of the input-parameter value (minus the null terminator). Use a library function, such as strlen() or stleng(), to determine the string length.
For input-parameter values that are in binary representation, the database server does not need to access the entry of the parameter-value length array.
Lengths are not needed in the following special cases:
- Input parameters whose data types (such as mi_integer) are passed with fixed lengths
- Input parameters with string values are passed in varying-length structures
  A varying-length structure holds its own data length.

Important: Even though there are some cases in which the database server does not read the length of the input-parameter value, it is recommended that you always specify lengths to maintain consistency of code.