Author here, a roaring bitmap could absolutely have been used! The concept is similar and it absolutely should have been mentioned. > Presuming user IDs are n

Author here, a roaring bitmap could absolutely have been used! The concept is similar and it absolutely should have been mentioned. > Presuming user IDs are non-sparse nonnegative integers (as SERIAL/BIGSERIAL pkeys usually are), I personally wanted to build a method that worked for textual content easily but with that constraint (which is valid and what I ended up doing in practice) a roaring bitmap definitely works! I want to give this a try in the future