Informix DataBlade API Programmer's Manual Executing User-Defined Routines

Within a DataBlade API module, you can use either of the following methods to call a UDR, as long as you know the name of the UDR you want to call:

• You can execute an SQL statement that invokes a registered UDR.
• You can directly call any UDR that resides in the same shared-object file.

You can call any registered UDR in an SQL statement. When your UDR is called in an SQL statement, the database server parses the statement and produces a query plan. It then automatically performs any routine resolution necessary and loads the shared-object file in which that user-defined routine resides into shared memory (if it is not already loaded) when it parses and compiles the SQL statement. For more information on how the database server executes a UDR in an SQL statement, see Executing a User-Defined Routine.

Within the DataBlade API, you can:

• execute SQL statements with the mi_exec() function.
• execute prepared SQL statements with the mi_exec_prepared_statement() function.

For example, the following call to mi_exec() sends the EXECUTE FUNCTION statement to the database server to execute the myfunc() user-defined function:

mi_exec(conn, "EXECUTE FUNCTION myfunc(5,5);",
	MI_QUERY_BINARY);

For more information on the use of mi_exec() and mi_exec_prepared_statement(), see Chapter 7, Establishing a Connection.

From within a C UDR, you can directly call another C function when the following conditions are met:

• At compile time, you know the name of the C function that you want to call.
• The C function resides in the same shared-object file as the calling UDR.

This C function can be a registered UDR. In Figure 9-9, assume that the func2() and func3() functions were registered as user-defined functions with the CREATE FUNCTION statement. The func3() user-defined function can directly call the func2() UDR because func3() and func2() reside in the same shared-object file, source1.so.

Figure 9-9 Calling a UDR Directly From Another UDR

If the UDR that you want to call is an overloaded routine, the database server executes the version of the UDR that resides in the same shared-object file. This UDR gets neither parameter casting nor a default MI_FPARAM structure. If no version of this UDR exists in the same shared-object file, you receive a runtime error. To execute UDRs in other shared-object files, use the Fastpath interface.