private void trackTimestamps(final ExtendedCell cell) {
      if (KeyValue.Type.Put.getCode() == cell.getTypeByte()) {
        earliestPutTs = Math.min(earliestPutTs, cell.getTimestamp());
      }
      timeRangeTracker.includeTimestamp(cell);
    }
Record the earlest Put timestamp. If the timeRangeTracker is not set, update TimeRangeTracker
to include the timestamp of this key
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreFileWriter.java