@HiveDecimalWritableVersionV1
  public void set(HiveDecimalWritable writable) {
    if (writable == null || !writable.isSet()) {
      fastReset();
      isSet = false;
    } else {
      fastSet(writable);
      isSet = true;
    }
  }
Set the writable's current value to the value in a another decimal writable.
<p>
If the supplied writable has a value, isSet() will return true.
storage-api/src/java/org/apache/hadoop/hive/serde2/io/HiveDecimalWritable.java