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
/**
		 * @return the parent query for the current report item
		 */
		protected BaseQueryDefinition getParentQuery( )
		{
			if ( queryStack.isEmpty( ) )
				return null;
			for ( int i = queryStack.size( ) - 1; i >= 0; i-- )
			{
				if ( queryStack.get( i ) instanceof BaseQueryDefinition )
					return (BaseQueryDefinition) queryStack.get( i );
			}
			return null;
		}
		/**
		 * @return the expression collection
		 */
		protected Collection getExpressions( )
		{
			return expressions;
		}
		/**
		 * @return a unique query name, based on a simple integer counter
		 */
		protected String createUniqueQueryName( )
		{
			queryCount++;
			return String.valueOf( queryCount );
		}
		/**