@Override
  public int hashCode() {
    if (signum == 0) {
      return 0;
    }
    return signum * (scale * 31 + unscaledValue.hashCode());
  }
Returns the hash code for this {@code Decimal128}. Note that two
{@code Decimal128} objects that are numerically equal but differ in scale
(like 2.0 and 2.00) will generally <i>not</i> have the same hash code. This
somewhat confusing behavior is, however, same as java.math.BigDecimal.

@return hash code for this {@code Decimal128}.
@see #equals(Object)
common/src/java/org/apache/hadoop/hive/common/type/Decimal128.java