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
*/
	protected ExecutionContext context;
	
	/**
	 * the max rows per query
	 */
	protected int maxRows = 0;
	IQueryContext queryContext;
	public ReportQueryBuilder( )
	{
		expressionUtil = new ExpressionUtil( );
		queryBuilder = new QueryBuilderVisitor( );
		
	}	
	/**
	 * @param report
	 *            the entry point to the report design
	 * @param context
	 *            the execution context
	 */
	public ReportQueryBuilder( Report report, ExecutionContext context )
	{
		expressionUtil = new ExpressionUtil( );
		queryBuilder = new QueryBuilderVisitor( );
		this.report = report;
		this.context = context;
		
		
		if( null != this.context )
		{