@Override
  public HiveDecimalWritable plus(HiveDecimalWritable t1, HiveDecimalWritable t2) {
    return VectorPTFEvaluatorHelper.plus(t1, t2);
  }
This class evaluates HiveDecimal sum() for a PTF group.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/ptf/VectorPTFEvaluatorDecimalSum.java