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
.sortsIterator( ) );
		}
		/**
		 * create sort array by giving GroupHandle
		 * 
		 * @param group
		 *            the GroupHandle
		 * @return the sort array
		 */
		protected ArrayList createSorts( GroupHandle group )
		{
			return createSorts( group.sortsIterator( ) );
		}
		/**
		 * create input parameter binding
		 * 
		 * @param handle
		 * @return
		 */
		protected IInputParameterBinding createParamBinding(
				ParamBindingHandle handle )
		{
			if ( handle.getExpression( ) == null )
				return null; 
			ScriptExpression expr = new ScriptExpression( handle
					.getExpression( ) );
			
			return new InputParameterBinding( handle.getParamName( ), expr );
		}
		/**