> I'm afraid that's a misunderstanding - my objections did not really go
> away. I'm just saying my claim that we're not messing with order of
> grouping keys is not entirely accurate, because we do that in one
> particular case.
>
> I still think we need to be careful when introducing new optimizations
> in this area - reordering the grouping keys by ndistinct, ORDER BY or
> whatever. In particular I don't think we should commit these patches
> that may quite easily cause regressions, and then hope some hypothetical
> future patch fixes the costing. Those objections still stand.
Pls, have a look at https://commitfest.postgresql.org/18/1706/
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.
--
Teodor Sigaev E-mail: teodor@sigaev.ru
WWW: http://www.sigaev.ru/