public List<String> getOutputColumnNames() {
    List<String> outputAggregationNames = getActualAggregationNames(step.isOutputPartial());
    List<String> outputColumnNames = new ArrayList<>();
    for (String funcName : outputAggregationNames) {
      outputColumnNames.add(funcName + "(" + getParametersString() + ")");
    }
    return outputColumnNames;
  }
Input of aggregation function. Currently, we only support one series in the aggregation
function.

<p>example: select sum(s1) from root.sg.d1; expression [root.sg.d1.s1] will be in this field.

<p>example: select sum(s1) from root.** group by level = 1; expression [root.sg.*.s1] may be in
this field if the data is in different DataRegion
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/parameter/AggregationDescriptor.java