presto-main/src/main/java/io/prestosql/type/setdigest/SetDigestStateFactory.java/GroupedSetDigestState/setDigest
class GroupedSetDigestState:        @Override
        public void setDigest(SetDigest value)
        {
            if (getDigest() != null) {
                size -= getDigest().estimatedInMemorySize();
            }
            size += value.estimatedInMemorySize();
            digests.set(groupId, value);
        }