Re: Removing unneeded self joins

Thank you for this partial review, I included your changes:

On 9/23/20 9:23 AM, David Rowley wrote:
> On Fri, 3 Apr 2020 at 17:43, Andrey Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru> wrote:
> Doing thing the way I describe will allow you to get rid of all the
> UniqueRelInfo stuff.
Thanks for the review and sorry for the late reply.
I fixed small mistakes, mentioned in your letter.
Also I rewrote this patch at your suggestion [1].
Because of many changes, this patch can be viewed as a sketch.

To change self-join detection algorithm I used your delta patch from
[2]. I added in the split_selfjoin_quals routine complex expressions
handling for demonstration. But, it is not very useful with current
infrastructure, i think.

Also I implemented one additional way for self-join detection algorithm:
if the join target list isn't contained vars from inner relation, then
we can detect self-join with only quals like a1.x=a2.y if check
innerrel_is_unique is true.
Analysis of the target list is contained in the new routine -
tlist_contains_rel_exprs - rewritten version of the build_joinrel_tlist
routine.

Also changes of the join_is_removable() routine is removed from the
patch. I couldn't understand why it is needed here.

Note, this patch causes change of one join.sql regression test output.
It is not a bug, but maybe fixed.

Applied over commit 4a071afbd0.

> [1]
https://www.postgresql.org/message-id/CAKJS1f8p-KiEujr12k-oa52JNWWaQUjEjNg%2Bo1MGZk4mHBn_Rg%40mail.gmail.com
[2]
https://www.postgresql.org/message-id/CAKJS1f8cJOCGyoxi7a_LG7eu%2BWKF9%2BHTff3wp1KKS5gcUg2Qfg%40mail.gmail.com

--
regards,
Andrey Lepikhov
Postgres Professional