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
if ( exprs != null )
			{
				Iterator iter = exprs.values( ).iterator( );
				while ( iter.hasNext( ) )
				{
					IBaseExpression expr = (IBaseExpression) iter.next( );
					addExpression( expr );
				}
			}
			finishVisit( query );
			return value;
		}
		/*
		 * (non-Javadoc)
		 * 
		 * @see org.eclipse.birt.report.engine.ir.ReportItemVisitor#visitTableItem(org.eclipse.birt.report.engine.ir.TableItemDesign)
		 */
		public Object visitTableItem( TableItemDesign table, Object value )
		{
			BaseQueryDefinition query = prepareVisit( table );
			for ( int i = 0; i < table.getColumnCount( ); i++ )
			{
				
				
			}
			if ( query == null )
			{
				handleTableBand( table.getHeader( ), value );
				handleTableBand( table.getFooter( ), value );
			}