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
public void selectResultSet( String displayName )
	{
		assert displayName != null;
		resultSetName = (String)mapDispNameToResultSetName.get( displayName );
		selectedColumns = null;
		currentResult = null;
	}
	
	public List getMetaData( ) throws EngineException
	{
		if ( resultMetaList == null )
		{
			resultMetaList = new ArrayList( );
			ResultMetaData metaData = null;
			if ( selectedColumns == null && instanceId != null )
			{
				currentResult = extract( );
				try
				{
					resultMetaList.add( currentResult.getResultMetaData( ) );
				}
				catch( BirtException be )
				{
					be.printStackTrace();
				}
			}
			
			if( selectedColumns == null )
			{