public double getDouble() {
    double seconds, nanos;
    if (bytesEmpty) {
      seconds = timestamp.toEpochSecond();
      nanos = timestamp.getNanos();
    } else {
      seconds = getSeconds();
      nanos = getNanos();
    }
    return seconds + nanos / 1000000000;
  }
@return double representation of the timestamp, accurate to nanoseconds
serde/src/java/org/apache/hadoop/hive/serde2/io/TimestampWritableV2.java