private Aggregation getCurrentAggregationBuffer(
      VectorAggregationBufferRow[] aggregationBufferSets,
      int aggregateIndex,
      int row) {
    VectorAggregationBufferRow mySet = aggregationBufferSets[row];
    Aggregation myagg = (Aggregation) mySet.getAggregationBuffer(aggregateIndex);
    return myagg;
  }
Value is explicitly (re)initialized in reset()
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/aggregates/VectorUDAFSumDecimal64.java