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: Dilip Kumar <dilipbalaut@gmail.com>
Cc: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.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: 2025-07-03T05:13:24Z
Lists: pgsql-hackers 
On Thu, Jul 3, 2025 at 10:26 AM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> On Wed, Jul 2, 2025 at 12:58 PM Zhijie Hou (Fujitsu)
> <houzj.fnst@fujitsu.com> wrote:
> >
>
> > During local testing, I discovered a bug caused by my oversight in assigning
> > the new xmin to slot.effective, which resulted in dead tuples remaining
> > non-removable until restart. I apologize for the error and have provided
> > corrected patches. Kindly use the latest patch set for performance testing.
>
> You changes related to write barrier LGTM, however I have question
> regarding below change, IIUC, in logical replication
> MyReplicationSlot->effective_xmin should be the xmin value which has
> been flushed to the disk, but here we are just setting "data.xmin =
> new_xmin;" and marking the slot dirty so I believe its not been yet
> flushed to the disk right?
>

Yes, because this is a physical slot and we need to follow
PhysicalConfirmReceivedLocation()/PhysicalReplicationSlotNewXmin().
The patch has kept a comment in advance_conflict_slot_xmin() as to why
it is okay not to flush the slot immediately.

-- 
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.