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
resultMetaList.add( resultItem );
	}
	
	public void selectColumns( String[] columnNames )
	{
		selectedColumns = columnNames;
		currentResult = null;
	}
	
	public IExtractionResults extract( ) throws EngineException
	{
		if ( currentResult != null )
			return currentResult;
		
		if( instanceId != null )
		{
			return extractByInstanceId( );
		}
		else if( resultSetName != null )
		{
			return extractByResultSetName( );
		}
		return null;
	}
	
	/*
	 * export result directly from result set name
	 */
	private IExtractionResults extractByResultSetName( ) throws EngineException
	{