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
if ( query != value )
			{
				return new IBaseQueryDefinition[]{ query };
			}
			return null;
		}
		/*
		 * (non-Javadoc)
		 * 
		 * @see org.eclipse.birt.report.engine.ir.ReportItemVisitor#visitTextItem(org.eclipse.birt.report.engine.ir.TextItemDesign)
		 */
		public Object visitTextItem( TextItemDesign text, Object value )
		{
			BaseQueryDefinition query = createQuery( text, value );
			HashMap exprs = text.getExpressions( );
			if ( exprs != null )
			{
				Iterator ite = exprs.entrySet( ).iterator( );
				while ( ite.hasNext( ) )
				{
					Map.Entry entry = (Map.Entry) ite.next( );
					assert entry.getValue( ) instanceof String;
					String newExpr = transformExpression( entry.getValue( ).toString( ), query, null );
					entry.setValue( newExpr );
				}				
			}
			finishVisit( text, query );
			if ( query != value )
			{
				return new IBaseQueryDefinition[]{ query };