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
/**
		 * finish the current visit. transform the expressions of the query.
		 * @param item
		 * @param query
		 */
		private void finishVisit( ReportItemDesign item, IBaseQueryDefinition query )
		{			
			if( query != null )
			{
				transformExpressions( item, query, null );
			}
		}
	}
	
	private int toDteFilterOperator( String modelOpr )
	{
		if ( modelOpr.equals( DesignChoiceConstants.FILTER_OPERATOR_EQ ) )
			return IConditionalExpression.OP_EQ;
		if ( modelOpr.equals( DesignChoiceConstants.FILTER_OPERATOR_NE ) )
			return IConditionalExpression.OP_NE;
		if ( modelOpr.equals( DesignChoiceConstants.FILTER_OPERATOR_LT ) )
			return IConditionalExpression.OP_LT;
		if ( modelOpr.equals( DesignChoiceConstants.FILTER_OPERATOR_LE ) )
			return IConditionalExpression.OP_LE;
		if ( modelOpr.equals( DesignChoiceConstants.FILTER_OPERATOR_GE ) )
			return IConditionalExpression.OP_GE;
		if ( modelOpr.equals( DesignChoiceConstants.FILTER_OPERATOR_GT ) )
			return IConditionalExpression.OP_GT;
		if ( modelOpr.equals( DesignChoiceConstants.FILTER_OPERATOR_BETWEEN ) )
			return IConditionalExpression.OP_BETWEEN;