@Override
    public float getProgress() throws IOException, InterruptedException {
      // This would be inaccurate if KVs are not uniformly-sized or we have performed a seek to
      // the start row, but better than nothing anyway.
      return 1.0f * count / in.getEntries();
    }
A private cache of the key value so it doesn't need to be loaded twice from the scanner.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/HFileInputFormat.java