On Sat, 12 Oct 2019 at 17:16, Andrew Gierth <and...@tao11.riddles.org.uk> wrote:
> >>>>> "Ivan" == Ivan Voras <ivo...@gmail.com> writes: > > Ivan> SELECT user1_id,user2_id FROM friend WHERE user1_id=42 OR > user2_id=42; > > To get friends of user 42: > > SELECT user1_id FROM friend WHERE user2_id=42 > UNION ALL > SELECT user2_id FROM friend WHERE user1_id=42; > > assuming you create the (user2_id,user1_id) index, this should get you > an Append of two index-only scans. We can use UNION ALL here rather than > UNION because the table constraints ensure there are no duplicates. > Thanks! That's a more elegant solution for my query than what I had in mind!
