@Override
 public Operator run() {
   List<AggregationFunctionGroupByOperator> aggregationFunctionOperatorList =
       new ArrayList<AggregationFunctionGroupByOperator>();
   for (AggregationFunctionGroupByPlanNode aggregationFunctionGroupByPlanNode :
       _aggregationFunctionGroupByPlanNodes) {
     aggregationFunctionOperatorList.add(
         (AggregationFunctionGroupByOperator) aggregationFunctionGroupByPlanNode.run());
   }
   return new MAggregationGroupByOperator(
       _indexSegment,
       _brokerRequest.getAggregationsInfo(),
       _brokerRequest.getGroupBy(),
       _projectionPlanNode.run(),
       aggregationFunctionOperatorList);
 }