presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/storage/FileStorageService.java/FileStorageService/getFileSystemPath
class FileStorageService:    public static File getFileSystemPath(File base, UUID shardUuid)
    {
        String uuid = shardUuid.toString().toLowerCase(ENGLISH);
        return base.toPath()
                .resolve(uuid.substring(0, 2))
                .resolve(uuid.substring(2, 4))
                .resolve(uuid + FILE_EXTENSION)
                .toFile();
    }