Robert Haas <robertmhaas@xxxxxxxxx> writes: > On Sun, Oct 18, 2009 at 1:59 PM, Jeff Janes <jeff.janes@xxxxxxxxx> wrote: >> Even if country.id is a primary or unique key? > Well, we currently don't have any logic for making inferences based on > unique constraints. Huh? http://archives.postgresql.org/pgsql-committers/2009-09/msg00159.php Admittedly it's just one case and there's lots more to be done, but it's more than nothing. So this is a *potential* argument for trying to trim subquery outputs. What I'm not sure about is whether there are common cases where this would be applicable below a non-flattenable subquery. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
