Horton

Re: Conflict detection for update_deleted in logical replication

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, shveta malik <shveta.malik@gmail.com>, vignesh C <vignesh21@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>
Date: 2025-07-22T22:20:57Z
Lists: pgsql-hackers 
On Mon, Jul 21, 2025 at 8:49 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Mon, Jul 21, 2025 at 11:27 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> > On Sun, Jul 20, 2025 at 9:00 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > >
> >
> > > If so, I agree
> > > with you, we don't need XIDs of other databases as logical WALSender
> > > will anyway won't process transactions in other databases, so we can
> > > exclude those. The function GetOldestActiveTransactionId() is called
> > > from two places in patch get_candidate_xid() and
> > > ProcessStandbyPSRequestMessage(). We don't need to care for XIDs in
> > > other databases at both places but care for
> > > Commit_Critical_Section_Phase when called from
> > > ProcessStandbyPSRequestMessage(). So, we probably need two parameters
> > > to distinguish those cases.
> >
> > Why do we need to include all XIDs even in the cases called from
> > ProcessStandbyPSRequestMessage()?
> >
>
> No, we don't need all XIDs even in the case of
> ProcessStandbyPSRequestMessage(). That is what I wrote: "The function
> GetOldestActiveTransactionId() is called from two places in patch
> get_candidate_xid() and ProcessStandbyPSRequestMessage(). We don't
> need to care for XIDs in other databases at both places ...". Am I
> missing something or you misread it?

Oh I misread it. Sorry for the noise.

>
> > I guess that there is no chance that
> > the changes happening on other (non-subscribed) databases could
> > conflict with something on the subscriber.
> >
>
> Right.

I've reviewed the 0001 patch and it looks good to me. The patch still
has XXX comments at several places. Do we want to keep all of them as
they are (i.e., as something like TODO or FIXME)?

Regards,

--
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com

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.