public long getSize() {
    File file = new File(filePath);
    if (file.exists()) {
      return file.length();
    } else {
      return 0;
    }
  }
Create a hardlink for the modification file. The hardlink with have a suffix like
".{sysTime}_{randomLong}"

@return a new ModificationFile with its path changed to the hardlink, or null if the origin
    file does not exist or the hardlink cannot be created.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/modification/v1/ModificationFileV1.java