Selective dequeue of messages unrelated to those already in a transaction.
805627Oct 20 2010 — edited Oct 20 2010Hello
In an AQ queue, I need to ensure that messages which are related to each other are processed sequentially.
For example, assume the queue is seeded with the four messages that have a business-related field called transaction reference (txn_ref) and two of the messages (1,3) belong to the same transaction (000001):
id | txn_ref |
------------
1 | 000001 |
2 | 000002 |
3 | 000001 |
4 | 000003 |
Assume also that I am running 4 threads/processes that wish to dequeue from this queue. The following should occur:
1. thread 1 dequeues message #1
2. thread 2 dequeues message #2
3. thread 3 dequeues message #4 (because message #3 is related to #1 and #1 has not yet completed).
4. thread 4 blocks waiting for a message
5. thread 1 commits its work for message #1
6. thread 4 (or perhaps thread 1) dequeues message #3.
My initial thought was that I could achieve this with a dequeue condition where the ENQ_TIME (enqueue time) is not later than any other ENQ_TIME of all the messages that have the same TXN_REF. But my problem is how to reference the TXN_REF of a message that I have not yet selected, in order to select it. e.g.
// Java API
String condition = "ENQ_TIME = (select min(ENQ_TIME) from AQ_TABLE1 where ??"; // where what?
dequeueOption.setCondition(condition);
Is it possible to achieve what I want here?
Edited by: user8264946 on Oct 19, 2010 9:03 PM
Edited by: user8264946 on Oct 19, 2010 9:04 PM