On Mon, May 6, 2024 at 12:24:41PM -0400, Robert Haas wrote: > Now that being said, I do also agree that the planner code is quite > hard to understand, for various reasons. I don't think the structure > of that code and the assumptions underlying it are as well-documented > as they could be, and neither do I think that all of them are optimal. > It has taken me a long time to learn as much as I know, and there is > still quite a lot that I don't know. And I also agree that the planner > does an unfortunate amount of in-place modification of existing > structures without a lot of clarity about how it all works, and an > unfortunate amount of data copying in some places, and even that the > partition-wise join code isn't all that it could be. But I do not > think that adds up to a conclusion that we should just be less > ambitious with planner changes. Indeed, I would like to see us do > more. There is certainly a lot of useful work that could be done. The > trick is figuring out how to do it without breaking too many things, > and that is not easy.
I agree with Robert. While writting the Postgres 17 release notes, I am excited to see the many optimizer improvements, and removing self-joins from that list will be unfortunate. I did write a blog entry in 2021 that suggested we could have optimizer aggressiveness control to allow for more expensive optimizations: https://momjian.us/main/blogs/pgblog/2021.html#May_14_2021 -- Bruce Momjian <br...@momjian.us> https://momjian.us EDB https://enterprisedb.com Only you can decide what is important to you.