@Override
  // Simplify vector by brute-force flattening noNulls and isRepeating
  // This can be used to reduce combinatorial explosion of code paths in VectorExpressions
  // with many arguments.
  public void flatten(boolean selectedInUse, int[] sel, int size) {
    flattenPush();
    if (isRepeating) {
      isRepeating = false;
      HiveDecimalWritable repeat = vector[0];
      if (selectedInUse) {
        for (int j = 0; j < size; j++) {
          int i = sel[j];
          vector[i].set(repeat);
        }
      } else {
        for (int i = 0; i < size; i++) {
          vector[i].set(repeat);
        }
      }
      flattenRepeatingNulls(selectedInUse, sel, size);
    }
    flattenNoNulls(selectedInUse, sel, size);
  }
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