@HiveDecimalWritableVersionV1
  public HiveDecimalV1 getHiveDecimal(int maxPrecision, int maxScale) {
     return HiveDecimalV1.enforcePrecisionScale(HiveDecimalV1.
             create(new BigInteger(internalStorage), scale),
         maxPrecision, maxScale);
  }
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