Horton

Re: Conflict detection for update_deleted in logical replication

Nisha Moond <nisha.moond412@gmail.com>

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From: Nisha Moond <nisha.moond412@gmail.com>
To: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
Cc: vignesh C <vignesh21@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, shveta malik <shveta.malik@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2025-04-17T06:10:21Z
Lists: pgsql-hackers 
On Wed, Mar 26, 2025 at 4:17 PM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> Here's a rebased version of the patch series.
>

Thanks for the patches.

While testing the GUC "max_conflict_retention_duration", I noticed a
behavior that seems to bypass its intended purpose.

On Pub, if a txn is stuck in the COMMIT phase for a long time, the
apply_worker on the sub keeps looping in wait_for_publisher_status()
until that Pub's concurrent txn completes its commit.
Due to this, the apply worker can't advance its
oldest_nonremovable_xid and keeps waiting for the Pub's txn to finish.
In such a case, even if the wait time exceeds the configured
max_conflict_retention_duration, conflict retention doesn't stop for
the apply_worker. The conflict info retention is stoppend only once
the Pub's txn is committed and the apply_worker moves to
wait_for_local_flush().

Doesn't this defeat the purpose of max_conflict_retention_duration?
The apply worker has exceeded the max wait time but still retains the
conflict info.
I think we should consider applying the same max time limit check
inside wait_for_publisher_status() as well.

--
Thanks,
Nisha

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.