I don't see why not to generate all possible orderings (keeping only the
cheapest path for each pathkey variant) and let the optimizer to sort it
out.
I'm assuming costing the full N! possible orderings would be
prohibitively expensive.
That's true, but for the first step we need to improve cost_sort and only then
try to find the best pathkeys order by optimal way.
- If the user requested that order, we assume it "somewhat
subjectively better" (by giving it a slightly reduced cost).
I don't think so. It's not a SQL way - DB should define the optimal way to
execute query.
--
Teodor Sigaev E-mail: teo...@sigaev.ru
WWW: http://www.sigaev.ru/
