@HiveDecimalWritableVersionV2
  public void mutateRemainder(HiveDecimalWritable decWritable) {
    if (!isSet || !decWritable.isSet) {
      isSet = false;
      return;
    }
    isSet =
        fastRemainder(decWritable, this);
  }
Allocate scratchLongs with HiveDecimal.SCRATCH_LONGS_LEN longs.
And, allocate scratch scratchBuffer with HiveDecimal.SCRATCH_BUFFER_LEN_BIG_INTEGER_BYTES bytes.
storage-api/src/java/org/apache/hadoop/hive/serde2/io/HiveDecimalWritable.java