presto-main/src/main/java/io/prestosql/operator/aggregation/state/QuantileDigestStateFactory.java/SingleQuantileDigestState/getEstimatedSize
class SingleQuantileDigestState:        @Override
        public long getEstimatedSize()
        {
            long estimatedSize = INSTANCE_SIZE;
            if (qdigest != null) {
                estimatedSize += qdigest.estimatedInMemorySizeInBytes();
            }
            return estimatedSize;
        }