Re: Inoptimal query plan for max() and multicolumn index

Vladimir Kulev <me@lightoze.net> wrote:

> # explain analyze select max(timestamp) from sms where number in
> ('5502712','5802693','5801981');

> According to planner cost estimations - it has enough data to
> understand that it is better to aggregate maximum from three
> subqueries. I suppose it's not a bug but not implemented feature

Yeah, you're hoping for an optimization which hasn't been
implemented.

I expect you're hoping for a plan similar to what this gives you?:

explain analyze select greatest(
  (select max(timestamp) from sms where number = '5502712'),
  (select max(timestamp) from sms where number = '5802693'),
  (select max(timestamp) from sms where number = '5801981'));

-Kevin