public void fill(HiveDecimal value) {
    isRepeating = true;
    isNull[0] = false;
    if (vector[0] == null) {
      vector[0] = new HiveDecimalWritable(value);
    }
    set(0, value);
  }
A vector of HiveDecimalWritable objects.

For high performance and easy access to this low-level structure,
the fields are public by design (as they are in other ColumnVector
types).
storage-api/src/java/org/apache/hadoop/hive/ql/exec/vector/DecimalColumnVector.java