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: Amit Kapila <amit.kapila16@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, vignesh C <vignesh21@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>
Date: 2025-08-21T08:39:11Z
Lists: pgsql-hackers 
On Thursday, August 21, 2025 2:01 PM shveta malik <shveta.malik@gmail.com> wrote:
> 
> On Wed, Aug 20, 2025 at 12:12 PM Zhijie Hou (Fujitsu)
> <houzj.fnst@fujitsu.com> wrote:
> >
> >
> > I agree. Here is V63 version which implements this approach.
> >
> 
> Thank You for the patches.
> 
> > The retention status is recorded in the pg_subscription catalog
> > (subretentionactive) to prevent unnecessary retention initiation upon
> > server restarts. The apply worker is responsible for updating this
> > flag based on the retention duration. Meanwhile, the column is set to
> > true when retain_dead_tuples is enabled or when creating a new
> > subscription with retain_dead_tuples enabled, and it is set to false when
> retain_dead_tuples is disabled.
> >
> 
> +1 on the idea.
> 
> Please find few initial testing feedback:

Thanks for the comments.

> 
> 1)
> When it stops, it does not resume until we restart th server. It keeps on waiting
> in wait_for_publisher_status and it never receives one.
> 
> 2)
> When we do: alter subscription sub1 set (max_conflict_retention_duration=0);
> 
> It does not resume in this scenario too.
> should_resume_retention_immediately() does not return true due to
> wait-status on publisher.

Fixed in the V64 patches.


> 3)
> AlterSubscription():
>  * retention will be stopped gain soon in such cases, and
> 
> stopped gain --> stopped again

Sorry, I missed this typo in V64, I will fix it in the next version.

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.