presto-main/src/main/java/io/prestosql/operator/aggregation/GenericAccumulatorFactory.java/DistinctingGroupedAccumulator/getEstimatedSize
class DistinctingGroupedAccumulator:        @Override
        public long getEstimatedSize()
        {
            return hash.getEstimatedSize() + accumulator.getEstimatedSize();
        }