public void sumValue(long value) {
      if (isNull) {
        sum = value;
        isNull = false;
      } else {
        if (Math.abs(sum) > nearDecimal64Max) {
          if (!usingRegularDecimal) {
            usingRegularDecimal = true;
            regularDecimalSum.deserialize64(sum, inputScale);
          } else {
            temp.deserialize64(sum, inputScale);
            regularDecimalSum.mutateAdd(temp);
          }
          sum = value;
        } else {
          sum += value;
        }
      }
    }
Value is explicitly (re)initialized in reset()
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/aggregates/VectorUDAFSumDecimal64ToDecimal.java