@Override
  public String resetCompactionCycleIndexInFileName(String fileName) {
    String[] parts = fileName.split("_");

    if (parts.length < 3) {
      logger.error("Not enough parts to have a middle index For Resseting Compaction Cycle Index in FileName: {}",
          fileName);
      throw new FileStoreException("Error while splitting file name: " + fileName,
          FileStoreLogAndIndexFileNamingConventionError);
    }

    parts[1] = "0";

    return String.join("_", parts);
  }
Resets the compaction cycle index in the file name.
@param fileName the file name to reset the compaction cycle index in.
@return the file name with the compaction cycle index reset to 0.
ambry-store/src/main/java/com/github/ambry/store/FileStore.java