>> 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: teodor@sigaev.ru
WWW: http://www.sigaev.ru/