public static TAggregationType getAggregationTypeByFuncName(String funcName) {
    if (isBuiltinAggregationName(funcName.toLowerCase())) {
      return TAggregationType.valueOf(funcName.toUpperCase());
    } else {
      // fallback to UDAF if no enum found
      return TAggregationType.UDAF;
    }
  }
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