private boolean checkPreExisting(FileSystem sourceFS, Path src, Path dest, Configuration conf)
    throws IOException {
    FileSystem destFS = dest.getFileSystem(conf);
    FileStatus destStatus = FileUtils.getFileStatusOrNull(destFS, dest);
    if (destStatus != null) {
      return (sourceFS.getFileStatus(src).getLen() == destStatus.getLen());
    }
    return false;
  }
@param src the source file.
@param dest the destination file.
@param conf the configuration
@return true if the file names match else returns false.
@throws IOException when any file system related call fails
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/DagUtils.java