Horton

Re: Conflict detection for update_deleted in logical replication

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Nisha Moond <nisha.moond412@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: 2025-08-26T09:02:10Z
Lists: pgsql-hackers 
On Tue, Aug 26, 2025 at 12:15 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Mon, Aug 25, 2025 at 5:05 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >

Some comments on latest patch
0001:

1.
+          <para>
+           Note that setting a non-zero value for this option could lead to
+           information for conflict detection being removed prematurely,
+           potentially missing some conflict detections.
+          </para>

We can improve this wording by saying "potentially incorrectly
detecting some conflict"

2.
@@ -1175,6 +1198,8 @@ AlterSubscription(ParseState *pstate,
AlterSubscriptionStmt *stmt,
  bool update_failover = false;
  bool update_two_phase = false;
  bool check_pub_rdt = false;
+ bool ineffective_maxconflretention = false;
+ bool update_maxretention = false;

For making variable names more consistent, better to change
'ineffective_maxconflretention' to 'ineffective_maxretention' so that
this will be more consistent with 'update_maxretention'

3.
+/*
+ * Report a NOTICE to inform users that max_conflict_retention_duration is
+ * ineffective when retain_dead_tuples is disabled for a subscription. An ERROR
+ * is not issued because setting max_conflict_retention_duration
causes no harm,
+ * even when it is ineffective.
+ */
+static void
+notify_ineffective_max_retention(bool update_maxretention)
+{
+ ereport(NOTICE,
+ errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ update_maxretention
+ ? errmsg("max_conflict_retention_duration has no effect when
retain_dead_tuples is disabled")
+ : errmsg("disabling retain_dead_tuples will render
max_conflict_retention_duration ineffective"));
 }

I really don't like to make a function for a single ereport, even if
this is being called from multiple places.


-- 
Regards,
Dilip Kumar
Google

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.