Horton

Re: Conflict detection for update_deleted in logical replication

shveta malik <shveta.malik@gmail.com>

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From: shveta malik <shveta.malik@gmail.com>
To: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.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>, shveta malik <shveta.malik@gmail.com>
Date: 2025-08-21T06:01:15Z
Lists: pgsql-hackers 
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:

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.

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

stopped gain --> stopped again

thanks
Shveta

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.