@HiveDecimalWritableVersionV2
  public void setFromLongAndScale(long longValue, int scale) {
    fastReset();
    isSet = fastSetFromLongAndScale(longValue, scale);
    if (!isSet) {
      fastReset();
    }
  }
Set the writable's current value to the long's value at a specified
scale.
<p>
Afterwards, the isSet() method will return true, unless conversion failed.
storage-api/src/java/org/apache/hadoop/hive/serde2/io/HiveDecimalWritable.java