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: 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>, shveta malik <shveta.malik@gmail.com>
Date: 2025-09-12T08:47:31Z
Lists: pgsql-hackers 
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:

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.

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?

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.