[hibernate-issues] [Hibernate-JIRA] Created: (HHH-3762) LockMode.UPGRADE and TABLE_PER_CLASS and PostgreSQL generates usupported SQL

[Dobes Vandermeer (JIRA)]

LockMode.UPGRADE and TABLE_PER_CLASS and PostgreSQL generates usupported SQL
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                 Key: HHH-3762
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3762
             Project: Hibernate Core
          Issue Type: Bug
          Components: core
    Affects Versions: 3.3.1
         Environment: Hibernate 3.3.1.GA, PostgreSQL 8.2, Hibernate-Annotations, Hibernate-EntityManager, Glassfish v2ur2, Windows Vista 64.bit
            Reporter: Dobes Vandermeer
            Priority: Minor


I created a class called Job and a few subclasses such as SendEmailJob, ProcessSubscriptionsJob, and so on.  I set the inheritance type to TABLE_PER_CLASS since the columns in each are quite different.  However, the worker that loads and executes the jobs is the same.

The worker was trying to use a piece of code like this:

@Timeout
public void timeout(Timer timer) {
    session.get(Job.class, (Long)timer.getInfo(), LockMode.UPGRADE);
}

PostgreSQL returned the following error:

org.postgresql.util.PSQLException: ERROR: SELECT FOR UPDATE/SHARE is not allowed with UNION/INTERSECT/EXCEPT

The workaround was to lock the object separately, so hibernate only tries to select .. for update from one table:

@Timeout
public void timeout(Timer timer) {
    Job job = session.get(Job.class, (Long)timer.getInfo(), LockMode.NONE);
    session.refresh(job, LockMode.UPGRADE); // Now there's just one table involved
}

A possible solution to this issue would be for hibernate to do this breakdown automatically when doing a get() on a TABLE_PER_CLASS superclass - i.e. it would ignore LockMode when fetching, but if LockMode is > UPGRADE it would call refresh() with that lock mode on the found object (if any) to lock it.  This does introduce an extra SELECT but I can't really think of another solution for this use case.


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