presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/storage/ShardRecoveryManager.java/ShardRecoveryManager/temporarySuffix
class ShardRecoveryManager:    private static File temporarySuffix(File file)
    {
        return new File(file.getPath() + ".tmp-" + UUID.randomUUID());
    }