Horton

RE: Conflict detection for update_deleted in logical replication

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

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From: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
To: shveta malik <shveta.malik@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, vignesh C <vignesh21@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>
Date: 2025-09-12T10:09:06Z
Lists: pgsql-hackers

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On Friday, September 12, 2025 4:48 PM shveta malik <shveta.malik@gmail.com> wrote:
> On Fri, Sep 12, 2025 at 8:55 AM Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>
> wrote:
> >
> >
> > I agree. Here is a V73 patch that will restart the worker if the
> > retention resumes. I also addressed other comments posted by Amit[1].
> >
> 
> Thanks for the patch. Few comments:

Thanks for the comments!

> 
> 1)
> There is a small window where worker can exit  while resuming retention and
> launcher can end up acessign stale worker info.
> 
> Lets say launcher is at a stage where it has fetched worker:
> w = logicalrep_worker_find(sub->oid, InvalidOid, false);
> 
> And after this point, before the launcher could do
> compute_min_nonremovable_xid(), the worker has stopped retention and
> resumed as well. Now the worker has exited but in
> compute_min_nonremovable_xid(), launcher will still use the worker-info
> fetched previously.

Thanks for catching this, I have fixed by computing the xid under
LogicalRepWorkerLock.

> 
> 2)
> 
>   if (should_stop_conflict_info_retention(rdt_data))
> +  {
> +    /*
> +     * Stop retention if not yet. Otherwise, reset to the initial phase
> +to
> +     * retry all phases. This is required to recalculate the current
> +wait
> +     * time and resume retention if the time falls within
> +     * max_retention_duration.
> +     */
> +    if (MySubscription->retentionactive)
> +      rdt_data->phase = RDT_STOP_CONFLICT_INFO_RETENTION;
> +    else
> +      reset_retention_data_fields(rdt_data);
> +
>     return;
> +  }
> 
> 
> 
> Shall we have an Assert( !MyLogicalRepWorker->oldest_nonremovable_xid)
> in 'else' part above?

Added.

Here is the V74 patch which addressed all comments.

Best Regards,
Hou zj

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.