Hello!
I have this method executed concurrently in many threads (MDBs), which
generates quite many OptimisticLockException.
I changed the datasource from HSQL to PostgreSQL and tried to add a
SELECT FOR UPDATE statement to act like a mutex
But why i keep getting OptimisticLockExceptions then?
did i do some mistake?
| @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
| public Process fetchProcess_real(int subsystem) {
|
| String lockQuery = "SELECT * FROM BPS_SUBSYSTEM WHERE id = :id
FOR UPDATE";
|
| String fetchQuery =
| "SELECT " +
| " p " +
| "FROM " +
| " Process AS p " +
| "WHERE " +
| " p.state = 0 AND " +
| " p.processQueue.id IN " +
| " (SELECT " +
| " pq.id " +
| " FROM " +
| " ProcessQueue AS pq " +
| " WHERE " +
| " (pq.subsystem.id = " +
| " (SELECT " +
| " s.id " +
| " FROM " +
| " Subsystem AS s " +
| " WHERE " +
| " (s.id = " + subsystem +
") AND " +
| " (s.connected = true) " +
| " ) " +
| " ) AND " +
| " (pq.connected = true) AND " +
| " (pq.curActiveProcesses <
pq.maxActiveProcesses) " +
| " ) " +
| "ORDER BY p.priority ASC, p.id ASC";
|
| Query nquery = em.createNativeQuery(lockQuery,Subsystem.class);
| nquery.setParameter("id",subsystem);
| Subsystem subsys = (Subsystem) nquery.getSingleResult();
|
|
| Query query = em.createQuery(fetchQuery);
| query.setMaxResults(1);
| List<Process> ProcessList = query.getResultList();
| if ((ProcessList == null) || ProcessList.isEmpty()) return null;
|
| Process p = ProcessList.get(0);
| ProcessQueue pq = p.getProcessQueue();
|
| p.use();
| pq.incrementActive();
|
| em.merge(p);
| em.merge(pq);
|
| return p;
| }
|
(ps the method is called always with the same parameter)
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