Question

How do I create PL/SQL function which waits for update on some row for specified timeout and then returns.

What I want to accomplish is – I have long running process which will update it’s status to ASYNC_PROCESS table by process_id. I need function which returns with true/false when this process has completed, but also I need this function to wait some time for this process complete, return on timeout or return imediately with true, when process has completed. I don’t want to use sleep(1 sec), because in such case I will be having 1 sec lag. I don’t want to use sleep(1 msec), because in such case I am spending cpu resources (and 1msec lag).

Is there a good way how experienced programmer would accomplish this?

That function will be called from .NET (So I need minimal lag between DB operation and .NET/UI)

THNX,
Beef

Answer 1

I think the most sensible thing to do in this case is to use update triggers on that ASYNC_PROCESS table.

You should also look into the DBMS_ALERT package. Here’s an edited excerpt from that doc:

Create an alert:

DBMS_ALERT.REGISTER('emp_table_alert');

Create a trigger on your table to fire the alert:

CREATE TRIGGER emptrig AFTER INSERT ON emp
BEGIN 
   DBMS_ALERT.SIGNAL('emp_table_alert', 'message_text'); 
END;

From your .net code, you can the use something that calls this:

DBMS_ALERT.WAITONE('emp_table_alert', :message, :status, :timeout); 

Make sure you read the docs for what :status and :timeout do.