In many cases you will want to provide users (or the application itself) with the ability to stop execution of a pipeline while it is in progress. For instance, you may want to give users a way out if they start the pipeline by mistake or if execution is taking longer than desired (maybe because many rows are involved).
Code the Cancel function in an appropriate script
Make sure that either the user or your application can execute this function (if appropriate) once the pipeline has started. When Cancel is executed, it stops the piping of any more rows after that moment.
Rows that have already been piped up to that moment may or may not be committed to the destination table, depending on the Commit property you specified when building your Pipeline object in the Data Pipeline painter. You will learn more about committing in the next section.
Test the result of the Cancel function
For more information on coding the Cancel function, see the PowerScript Reference.
The following example uses a command button to let users cancel pipeline execution in the order entry application.
Providing a CommandButton When creating the w_sales_extract window, include a CommandButton control named cb_stop. Then write code in a few of the application’s scripts to enable this CommandButton when pipeline execution starts and to disable it when the piping is done.
Calling the Cancel function Next write a script for the Clicked event of cb_stop. This script calls the Cancel function and tests whether or not it worked properly:
IF iuo_pipe_logistics.Cancel() = 1 THEN
Beep (1)
To cancel pipeline execution:
MessageBox("Operation Status", &
"Piping stopped (by your request).")
ELSE
Beep (1)
MessageBox("Operation Status", &
"Error when trying to stop piping.", &
Exclamation!)
END IF
Together, these features let a user of the application click the cb_stop CommandButton to cancel a pipeline that is currently executing.
