[hibernate-issues] [Hibernate-JIRA] Created: (HHH-3931) setMaxResults overwritten by NULL after set to 2 by getSingleResult()

[dm san (JIRA)]

setMaxResults overwritten by NULL after set to 2 by getSingleResult()
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                 Key: HHH-3931
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3931
             Project: Hibernate Core
          Issue Type: Bug
          Components: core
    Affects Versions: 3.3.1
            Reporter: dm san


This is where i create a query and call getSingleResult()
  
// This is in my project

            Query query = em.createQuery(SELECT_CLAUSE + "where ed.id=?1"); // select clause has left join fetch
            //query.setFirstResult(0).setMaxResults(2);
            query.setParameter(1, id);
            ABCD ede = (ABCD) query.getSingleResult(); // ABCD is some Entity


Method getSingleResult which sets the Max result to 2 (code -query.setMaxResults( 2 ) ) and then calls query.list() for answer

Class - org.hibernate.ejb.QueryImpl (JAR - hibernate-entitymanager-3.4.0.GA)
public Object getSingleResult() {
      try {
         List result;
         /* Avoid OOME if the list() is huge (user faulty query) by limiting the query to 2 elements max */
         //FIXME: get rid of this impl binding (HHH-3432)
         if ( query instanceof AbstractQueryImpl ) {
            if (maxResults != 1) query.setMaxResults( 2 ); //avoid OOME if the list is huge
            result = query.list();
            if ( maxResults != -1 ) {
               query.setMaxResults( maxResults ); //put back the original value
            }
            else {
               AbstractQueryImpl queryImpl = AbstractQueryImpl.class.cast( query );
               queryImpl.getSelection().setMaxRows( null );
            }
...
...// Code not required
...
   }


So when getSingleResult is called, it sets the max rows to 2. Now the problem is maxResult always gets overwritten by null.

queryParametersToUse = queryParameters.createCopyUsing( selection ); - this new selection object copies over Fetchsize and Timeout but not maxResults. Hence the new queryParameters does not have value 2.
There is a log warning ( log.warn( "firstResult/maxResults specified with collection fetch; applying in memory!" );) about it but i could not understand it. (is it trying to say if i have join fetch in my query, it would not use maxRows previously set. If yes, what should I do to setMaxResult with fetch)

Class - org.hibernate.hql.ast.QueryTranslatorImpl (JAR -hibernate-core-3.3.1.GA.jar)

public List list(SessionImplementor session, QueryParameters queryParameters)
         throws HibernateException {
       log.warn("Call in QuertTranslatorImpl Method Entry");
      // Delegate to the QueryLoader...
      errorIfDML();
      QueryNode query = ( QueryNode ) sqlAst;
      boolean hasLimit = queryParameters.getRowSelection() != null && queryParameters.getRowSelection().definesLimits();
      boolean needsDistincting = ( query.getSelectClause().isDistinct() || hasLimit ) && containsCollectionFetches();
      QueryParameters queryParametersToUse;
      if ( hasLimit && containsCollectionFetches() ) {
         log.warn( "firstResult/maxResults specified with collection fetch; applying in memory!" );
         RowSelection selection = new RowSelection();
         selection.setFetchSize( queryParameters.getRowSelection().getFetchSize() );
         selection.setTimeout( queryParameters.getRowSelection().getTimeout() );
         //selection.setMaxRows(queryParameters.getRowSelection().getMaxRows()); // If i include this line,everything works fine as Maxresults is also copied over
         queryParametersToUse = queryParameters.createCopyUsing( selection );
      }
      else {
         queryParametersToUse = queryParameters;
      }

      List results = queryLoader.list( session, queryParametersToUse );
...
...// Code not required
...

}

I have also posted in userforums:
https://forum.hibernate.org/viewtopic.php?f=1&t=997131&p=2412373#p2412373

Thank you..

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