On 4 November 2016 at 14:41, Merlin Moncure <mmonc...@gmail.com> wrote: > On Fri, Nov 4, 2016 at 8:08 AM, Kim Rose Carlsen <k...@hiper.dk> wrote: >> The nulls are generated by something like this >> SELECT c.circuit_id, >> cc.customer_id >> FROM circuit AS c >> LEFT JOIN circuit_customer AS cc >> ON c.circuit_id = cc.circuit_id >> >> To make a magic '0' customer we would be required to use >> COALESCE(cc.customer_id, '0') >> I dont think the optimizer will do anything clever with the '0' we have >> computed from null. > > It would if you explicitly indexed it as such; > CREATE INDEX ON circuit_customer((COALESCE(customer_id, '0'));
Merlin, it's a LEFT JOIN. There probably are no NULLs in the circuit_customer.customer_id column, so that COALESCE isn't going to achieve anything at all. I haven't been following this particular discussion in detail, so unfortunately I can't contribute more than that remark at the moment. -- If you can't see the forest for the trees, Cut the trees and you'll see there is no forest. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
