private void iterateNoNullsWithAggregationSelection(
      VectorAggregationBufferRow[] aggregationBufferSets,
      int aggregateIndex,
      TimestampColumnVector inputVector,
      int batchSize) {
      for (int i=0; i < batchSize; ++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