PG is doing the smart thing; it's optimizing for the common case of short IN/NOT IN literals in SQL queries. Simple arrays have much better constant factors. I

PG is doing the smart thing; it's optimizing for the common case of short IN/NOT IN literals in SQL queries. Simple arrays have much better constant factors. If the clause is a subselect (like yours) and is also an actual table (unlike yours), it will be smart and rewrite it as a JOIN, which will generally have better complexity if the indexes are correct.