Bug 122854 There is redundant columns in "available columns" list in "export data" dialog.
Description: There is redundant columns in "available columns" list in "export data" dialog. Steps to reproduce: 1. Preview attached design in web viewer. 2. Select the table and click on "export" button. 3. There is a "detail" column name in "available columns" list which is not data set column.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/ReportQueryBuilder.java
protected HashMap queryIDs;
		/**
		 * a collection of all the queries
		 */
		protected Collection queries;
		
		
		/**
		 * the query stack. The top stores the query that is currently prepared.
		 * Needed because we could have nested queries
		 */
		protected LinkedList queryStack = new LinkedList( );
		/**
		 * the total number of queries created in this report
		 */
		protected int queryCount = 0;
		/**
		 * a collection of the expressions on the CURRENT query
		 */
		protected Collection expressions;
		/**
		 * the expression stack. This is a link list of collections, not a
		 * link-list of individual expressions.
		 */
		protected LinkedList expressionStack = new LinkedList( );
		/**
		 * entry point to the report
		 */
		protected Report report;
		/**