On Thu, Oct 19, 2023 at 6:16 AM Andrei Lepikhov <a.lepik...@postgrespro.ru> wrote: > On 19/10/2023 01:50, Alexander Korotkov wrote: > > This query took 3778.432 ms with self-join removal disabled, and > > 3756.009 ms with self-join removal enabled. So, no measurable > > overhead. Similar to the higher number of joins. Can you imagine > > some extreme case when self-join removal could introduce significant > > overhead in comparison with other optimizer parts? If not, should we > > remove self_join_search_limit GUC? > Thanks, > It was Zhihong Yu who worried about that case [1]. And my purpose was to > show a method to avoid such a problem if it would be needed. > I guess the main idea here is that we have a lot of self-joins, but only > few of them (or no one) can be removed. > I can't imagine a practical situation when we can be stuck in the > problems here. So, I vote to remove this GUC.
I've removed the self_join_search_limit. Anyway there is enable_self_join_removal if the self join removal algorithm causes any problems. I also did some grammar corrections for the comments. I think the patch is getting to the committable shape. I noticed some failures on commitfest.cputube.org. I'd like to check how this version will pass it. ------ Regards, Alexander Korotkov
0001-Remove-useless-self-joins-v46.patch
Description: Binary data
