Horton

Re: Conflict detection for update_deleted in logical replication

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
Cc: Nisha Moond <nisha.moond412@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, shveta malik <shveta.malik@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, vignesh C <vignesh21@gmail.com>
Date: 2025-08-25T11:35:48Z
Lists: pgsql-hackers 
On Mon, Aug 25, 2025 at 10:06 AM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> Attach the V65 patch set which addressed above and
> Shveta's comments[1].
>

A few comments on 0001:
1.
- if (opts.retaindeadtuples)
- CheckSubDeadTupleRetention(true, !sub->enabled, NOTICE);
+ CheckSubDeadTupleRetention(true, !sub->enabled, NOTICE,
+    opts.retaindeadtuples,
+    retention_active, false,
+    sub->maxconflretention);

  /*
  * Notify the launcher to manage the replication slot for
@@ -1434,6 +1487,20 @@ AlterSubscription(ParseState *pstate,
AlterSubscriptionStmt *stmt,

  check_pub_rdt = opts.retaindeadtuples;
  retain_dead_tuples = opts.retaindeadtuples;
+
+ ineffective_maxconflretention = (!opts.retaindeadtuples &&
+ sub->maxconflretention);

Why can't we handle this special ineffective_maxconflretention case
inside CheckSubDeadTupleRetention? If so, then we can directly give
the NOTICE in case of SUBOPT_MAX_CONFLICT_RETENTION_DURATION without
having a separate notify_ineffective_max_retention() function.

2.
- if (sub->retaindeadtuples && can_advance_xmin)
+ if (sub->retaindeadtuples && sub->retentionactive &&
+ can_advance_xmin)

This coding pattern looks odd, you can have one condition per line.

3. Are we setting retention_inactive in launcher.c to true ever?

4.
this is because the launcher assigns
+ * the initial oldest_nonremovable_xid after the apply worker updates the
+ * catalog (see resume_conflict_info_retention).

I don't see resume_conflict_info_retention in 0001, so I couldn't make
sense of this part of the comment.

-- 
With Regards,
Amit Kapila.

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.