Bug 177504 Engine doesn't provide SubQuery for extended item
Engine doesn't provide SubQuery for extended item, so chart can't use container's binding to execute the query. If possible, engine could provide an option for extended item to choose whether engine could create the query, so extended item won't create SubQuery by itself.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/ReportQueryBuilder.java
String column = filterExpr;
			int dteOpr = ModelDteApiAdapter.toDteFilterOperator( filterOpr );
			String operand1 = handle.getValue1( );
			String operand2 = handle.getValue2( );
			return new FilterDefinition( new ConditionalExpression( column,
					dteOpr, operand1, operand2 ) );
		}
		/**
		 * create a filter array given a filter condition handle iterator
		 * 
		 * @param iter
		 *            the iterator
		 * @return filter array
		 */
		private ArrayList createFilters( Iterator iter )
		{
			ArrayList filters = new ArrayList( );
			if ( iter != null )
			{
				while ( iter.hasNext( ) )
				{
					FilterConditionHandle filterHandle = (FilterConditionHandle) iter
							.next( );
					IFilterDefinition filter = createFilter( filterHandle );
					filters.add( filter );
				}
			}
			return filters;
		}
		/**