@HiveDecimalWritableVersionV1
  @Override
  public int compareTo(HiveDecimalWritableV1 that) {
    return getHiveDecimal().compareTo(that.getHiveDecimal());
  }
Get a OldHiveDecimal instance from the writable and constraint it with maximum precision/scale.

@param maxPrecision maximum precision
@param maxScale maximum scale
@return OldHiveDecimal instance
storage-api/src/java/org/apache/hadoop/hive/serde2/io/HiveDecimalWritableV1.java