private void iterateNoSelectionHasNulls(
      Aggregation myagg,
      long[] vector,
      int batchSize,
      boolean[] isNull) {

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