private void iterateHasNullsWithAggregationSelection(
      VectorAggregationBufferRow[] aggregationBufferSets,
      int aggregateIndex,
      TimestampColumnVector inputVector,
      int batchSize,
      boolean[] isNull) {

      for (int i=0; i < batchSize; ++i) {
        if (!isNull[i]) {
          Aggregation myagg = getCurrentAggregationBuffer(
            aggregationBufferSets,
            aggregateIndex,
            i);
          myagg.sumValue(inputVector.getDouble(i));
        }
      }
    }
Value is explicitly (re)initialized in reset()
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/aggregates/VectorUDAFSumTimestamp.java