On Tue, 2004-04-27 at 17:27, Vitaly Belman wrote: > Hello pgsql-performance, > > I discussed the whole subject for some time in DevShed and didn't > achieve much (as for results). I wonder if any of you guys can help > out: > > http://forums.devshed.com/t136202/s.html
You're taking the wrong approach. Rather than using a select query to ensure that the book_id is distinct, add a constraint to the table so that is guaranteed. CREATE UNIQUE INDEX bv_bookgeneres_unq ON bv_bookgenres(book_id, genre_id); Now you can do a simple join (Drop the DISTINCT keyword) and achieve the same results. The point is that a book cannot be of a certain genre more than once. Without the distinct, this should take a matter of a few milliseconds to execute. ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings