public void sumValueNoNullCheck(long value) {
      sum += value;
      if (Math.abs(sum) > outputDecimal64AbsMax) {
        isOverflowed = true;
      }
    }
Value is explicitly (re)initialized in reset()
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/aggregates/VectorUDAFSumDecimal64.java