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
context.getLocale( ) );
			if ( ret == null )
			{
				logger.log( Level.SEVERE, "get resource error, resource key:" 
						+ resourceKey + " Locale:" 
						+ context.getLocale( ).toString( ) );
				return text;
			}
			return ret;
		}
		/**
		 * create one Filter given a filter condition handle
		 * 
		 * @param handle
		 *            a filter condition handle
		 * @return the filter
		 */
		private IFilterDefinition createFilter( FilterConditionHandle handle )
		{
			String filterExpr = handle.getExpr( );
			if ( filterExpr == null || filterExpr.length( ) == 0 )
				return null; 
			
			String filterOpr = handle.getOperator( );
			if ( filterOpr == null || filterOpr.length( ) == 0 )
				return new FilterDefinition( new ScriptExpression( filterExpr ) );
			/*
			 * has operator defined, try to convert filter condition to
			 * operator/operand style column filter with 0 to 2 operands
			 */