On Fri, Oct 28, 2016 at 10:29 AM, Kim Rose Carlsen <krc@xxxxxxxx> wrote: > Hi > > I was wondering if there is a way to hint that two columns in two different > tables IS NOT DISTINCT FROM each other. So that the optimizer may assume if > table_a.key = 'test' THEN table_b.key = 'test' . > > The equals operator already does this but it does not handle NULLS very well > (or not at all). And it seems IS NOT DISTINCT FROM is not indexable and > doesn't establish the same inference rules as equals. The whole idea behing Postgres' query planner is that you don't have to use any hints. Late model versions of postgres handle nulls fine, but nulls are never "equal" to anything else. I.e. where xxx is null works with indexes. Where x=y does not, since null <> null. Suggestion for getting help, put a large-ish aka production sized amount of data into your db, run your queries with explain analyze and feed them to https://explain.depesz.com/ and post the links here along with the slow queries. A lot of times the fix is non-obvious if you're coming from another db with a different set of troubleshooting skills for slow queries. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
