Re: Removing unneeded self joins

On Thu, Feb 13, 2025 at 1:00 AM Alexander Korotkov <aekorotkov@gmail.com> wrote:
>
> On Tue, Feb 11, 2025 at 5:31 PM Alena Rybakina
> <a.rybakina@postgrespro.ru> wrote:
> > Hi! Thank you for the work with this subject, I think it is really
> > important.
> >
> > On 10.02.2025 22:58, Alexander Korotkov wrote:
> > > Hi!
> > >
> > > On Mon, Feb 10, 2025 at 7:19 AM Andrei Lepikhov <lepihov@gmail.com> wrote:
> > >> On 9/2/2025 18:41, Alexander Korotkov wrote:
> > >>> Regarding adjust_relid_set() and replace_relid().  I think they are
> > >>> now strictly equivalent, except for the case then old relid is given
> > >>> and not found.  In this case adjust_relid_set() returns the original
> > >>> relids while replace_relid() returns a copy.  The behavior of
> > >>> adjust_relid_set() appears more desirable as we don't need extra
> > >>> copying when no modification is done.  So, I've replaced all
> > >>> replace_relid() with adjust_relid_set().
> > >> Ok, I glanced into it, and it makes sense to merge these routines.
> > >> I think the comment to adjust_relid_set() should be arranged, too. See
> > >> the attachment for a short variant of such modification.
> > >>> Also, I did some grammar correction to your new comment in tests.
> > >> Thanks!
> > > I've further revised adjust_relid_set() header comment.
> > >
> > > Looking back to the work done since previous attempt to commit this to
> > > pg17, I can highlight following.
> > > 1) We're now using more of existing infrastructure including
> > > adjust_relid_set() and ChangeVarNodes().  The most of complexity is
> > > still there though.
> > > 2) We've checked few ways to further simplify this patch.  But yet the
> > > current way still feels to be best possible.
> > > 3) For sure, several bugs were fixed.
> > >
> > > I think we could give it another chance for pg18 after some further
> > > polishing (at least commit message still needs to be revised).  Any
> > > thoughts on this?  Tom?
> > >
> > I didn't find any mistakes, I just have a refactoring remark. I think
> > the part where we add non-redundant expressions with the
> > binfo_candidates, jinfo_candidates
> > check can be moved to a separate function, otherwise the code is very
> > repetitive in this place. I did it and attached diff file
>
> Thank you.  I've integrated that into a patch.  However, I've to
> change keep_rinfo_list to be passed by pointer to
> add_non_redundant_clauses(), because it might be changed in
> distribute_restrictinfo_to_rels().  Without that there is a case of
> duplicated clause in regression tests.
>
> I've changed 'inner' and 'outer' vise versa in
> remove_self_joins_one_group() for better readability (I believe that
> was discussed upthread but lost).  Also, I did a round of improvement
> for comments and commit message.

I've corrected some spelling error reported by Alexander Lakhin
privately to me.  Also, I've revised comments around ChangeVarNodes()
and ChangeVarNodesExtended().  I'm going to continue nitpicking this
patch during next couple days then push it if no objections.

------
Regards,
Alexander Korotkov
Supabase