Horton

Re: Conflict detection for update_deleted in logical replication

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Xuneng Zhou <xunengzhou@gmail.com>, shveta malik <shveta.malik@gmail.com>, vignesh C <vignesh21@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2025-05-29T03:25:48Z
Lists: pgsql-hackers 
On Tue, May 27, 2025 at 11:45 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Mon, May 26, 2025 at 12:46 PM Zhijie Hou (Fujitsu)
> <houzj.fnst@fujitsu.com> wrote:
> >
> > On Sun, May 25, 2025 at 4:36 PM Dilip Kumar wrote:
> >
> > >
> > > I am thinking can't we make it more deterministic such that when we
> > > get the status first time if we find some transactions that are in
> > > commit phase then we should just wait for those transaction to get
> > > committed?  One idea is to get the list of xids in commit phase and
> > > next time when we get the list we can just compare and in next status
> > > if we don't get any xids in commit phase which were in commit phase
> > > during previous status then we are done.  But not sure is this worth
> > > the complexity?  Mabe not but shall we add some comment explaining the
> > > case and also explaining why this corner case is not harmful?
> >
> > I also think it's not worth the complexity for this corner case which is
> > rare.
>
> Yeah, complexity is one part, but I feel improving such less often
> cases could add performance burden for more often cases where we need
> to either maintain and invalidate the cache on the publisher or send
> the list of all such xids to the subscriber over the network.

Yeah, that's a valid point.

> > So, I have added some comments in wait_for_publisher_status() to
> > mention the same.
> >
>
> I agree that at this stage it is good to note down in comments, and if
> we face such cases often, then we can improve it in the future.

+1

-- 
Regards,
Dilip Kumar
Google

Commits

  1. Fix intermittent BF failures in 035_conflicts.

  2. Resume conflict-relevant data retention automatically.

  3. Fix intermittent test failure introduced in 6456c6e2c4.

  4. Fix Coverity issue reported in commit a850be2fe.

  5. Add test to prevent premature removal of conflict-relevant data.

  6. Post-commit review fixes for 228c370868.

  7. Add max_retention_duration option to subscriptions.

  8. Detect and report update_deleted conflicts.

  9. Preserve conflict-relevant data during logical replication.

  10. Integrate FullTransactionIds deeper into two-phase code

  11. Improve checks for GUC recovery_target_timeline

  12. Prevent excessive delays before launching new logrep workers.

  13. Keep WAL segments by slot's last saved restart LSN

  14. Rework some code handling pg_subscription data in psql and pg_dump

  15. Use generateClonedIndexStmt to propagate CREATE INDEX to partitions.