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/api/impl/DataExtractionTask.java
return null;
			}
			else
			{
				metaData = new ResultMetaData( null,
						selectedColumns );
				resultMetaList.add( metaData );
			}
		}
		return resultMetaList;
	}
	
	public List getResultSetList( ) throws EngineException
	{	
		if (resultMetaList == null) 
		{
			if( isMetaDataPrepared == false )
			{
				prepareMetaData( );
			}
			
			resultMetaList = new ArrayList();
			String dispName = null;
			IBaseQueryDefinition query = null;
			if( instanceId != null )
			{
				ReportItemDesign reportItem = (ReportItemDesign)report.getReportItemByID( 
						instanceId.getComponentID( ) );
				dispName = (String)mapReportItemToDisplayName.get( reportItem );
				query = reportItem.getQuery( );