Bug 145478 Unable "Select Value" in the Join data set's filter
Step to reproduce: 1.new a join data set(please use the attached file) 2.right click the dataset and click the Edit 3.go to the Filter pane and set a filer 4.click the list of Value1 Actual result: A warning pop up and cant select Value.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/data/ui/util/DataSetProvider.java
* @param newColumnNameSet
	 * @param columnName
	 * @param index
	 * @return
	 */
	private String getUniqueName( HashSet orgColumnNameSet,
			HashSet newColumnNameSet, String columnName, int index )
	{
		String newColumnName;
		if ( columnName == null
				|| columnName.trim( ).length( ) == 0
				|| newColumnNameSet.contains( columnName ) )
		{
			
			if ( columnName == null || columnName.trim( ).length( ) == 0 )
				newColumnName = UNNAME_PREFIX
						+ RENAME_SEPARATOR + String.valueOf( index + 1 );
			else
				newColumnName = columnName
						+ RENAME_SEPARATOR + String.valueOf( index + 1 );
			int i = 1;
			while ( orgColumnNameSet.contains( newColumnName )
					|| newColumnNameSet.contains( newColumnName ) )
			{
				newColumnName += String.valueOf( RENAME_SEPARATOR ) + i;
				i++;
			}
		}
		else
		{