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: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, shveta malik <shveta.malik@gmail.com>, vignesh C <vignesh21@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2025-07-01T05:01:56Z
Lists: pgsql-hackers 
On Mon, Jun 30, 2025 at 6:59 PM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> On Mon, Jun 30, 2025 at 7:22 PM Amit Kapila wrote:
> >

I was looking at 0001, it mostly looks fine to me except this one
case.  So here we need to ensure that commits must be acquired after
marking the flag, don't you think we need to ensure strict statement
ordering using memory barrier, or we think it's not required and if so
why?

RecordTransactionCommitPrepared()
{
..
+ MyProc->delayChkptFlags |= DELAY_CHKPT_IN_COMMIT;
+
+ /*
+ * Note it is important to set committs value after marking ourselves as
+ * in the commit critical section (DELAY_CHKPT_IN_COMMIT). This is because
+ * we want to ensure all transactions that have acquired commit timestamp
+ * are finished before we allow the logical replication client to advance
+ * its xid which is used to hold back dead rows for conflict detection.
+ * See maybe_advance_nonremovable_xid.
+ */
+ committs = GetCurrentTimestamp();
}

-- 
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.