public List<Type> buildSpillTypes() {
    ArrayList<Type> types = new ArrayList<>(groupByOutputTypes);
    for (GroupedAggregator groupedAggregator : groupedAggregators) {
      // types.add(groupedAggregator.getSpillType());
    }
    return types;
  }
building hash sorted results requires memory for sorting group IDs. This method returns size of
that memory requirement.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/source/relational/aggregation/grouped/builder/InMemoryHashAggregationBuilder.java