private void iterateNoSelectionNoNulls(
      Aggregation myagg,
      long[] vector,
      int batchSize) {
    if (myagg.isNull) {
      myagg.sum = 0;
      myagg.isNull = false;
    }

    for (int i=0;i<batchSize;++i) {
      long value = vector[i];
      myagg.sumValueNoCheck(value);
    }
  }
Value is explicitly (re)initialized in reset()
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/aggregates/VectorUDAFSumDecimal64ToDecimal.java