Bug 182895 Support sort on Level attribute.
Currently in OLAP engine we only support sort on level key value. We should go ahead to support sort on level attribute value.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/olap/query/view/QueryExecutor.java
MeasureNameManager manager, StopSign stopSign ) throws IOException, BirtException
	{
		AggregationDefinition[] aggrDefns = prepareCube( executor.getCubeQueryDefinition( ),
				manager.getCalculatedMembers( ) );
		if ( aggrDefns == null || aggrDefns.length == 0 )
			return null;
		IDocumentManager documentManager = getDocumentManager( executor );
		ICube cube = loadCube( documentManager, executor );
		CubeQueryValidator.validateCubeQueryDefinition( executor.getCubeQueryDefinition( ), view,
				cube,
				manager.getCalculatedMembers( ) );
		CubeQueryExecutorHelper cubeQueryExcutorHelper = new CubeQueryExecutorHelper( cube,
				executor.getComputedMeasureHelper( ) );
		cubeQueryExcutorHelper.addJSFilter( executor.getDimensionFilterEvalHelpers( ) );
		populateAggregationSort( executor, cubeQueryExcutorHelper, true );
		populateAggregationSort( executor, cubeQueryExcutorHelper, false );
		IAggregationResultSet[] rs = null;
		cubeQueryExcutorHelper.setBreakHierarchy( executor.getCubeQueryDefinition( )
				.getFilterOption( ) == 0 );
		
		if ( executor.getContext( ).getMode( ) == DataEngineContext.MODE_GENERATION )
		{
			rs = populateRs( executor, aggrDefns, cubeQueryExcutorHelper, true );
		}
		else if ( executor.getContext( ).getMode( ) == DataEngineContext.DIRECT_PRESENTATION )
		{
			rs = populateRs( executor, aggrDefns, cubeQueryExcutorHelper, false );
		}
		else if ( executor.getContext( ).getMode( ) == DataEngineContext.MODE_PRESENTATION )
		{