>> I tried to attack the cost_sort() issues and hope on that basis we can solve
>> problems with 0002 patch and improve incremental sort patch.
>>
>
> OK, will do. Thanks for working on this!
I hope, now we have a better cost_sort(). The obvious way is a try all
combination of pathkeys in get_cheapest_group_keys_order() and choose cheapest
one by cost_sort(). But it requires N! operations and potentially could be very
expensive in case of large number of pathkeys and doesn't solve the issue with
user-knows-what-he-does pathkeys. We could suggest an order of pathkeys as patch
suggests now and if cost_sort() estimates cost is less than 80% (arbitrary
chosen) cost of user-suggested pathkeys then it use our else user pathkeys.
--
Teodor Sigaev E-mail: teodor@sigaev.ru
WWW: http://www.sigaev.ru/