Re: Removing unneeded self joins - Mailing list pgsql-hackers

On 13.02.2025 02:00, Alexander Korotkov wrote:

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.

On 15.02.2025 12:19, Alexander Korotkov wrote:

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.

I agree with your corrections and for me patch looks good.

-- 
Regards,
Alena Rybakina
Postgres Professional