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: Amit Kapila <amit.kapila16@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, vignesh C <vignesh21@gmail.com>, shveta malik <shveta.malik@gmail.com>
Date: 2025-08-25T06:39:33Z
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].
>

Thank You for the patches, please find a few comments on v64 itself (I
think valid on v65 as well):

1) in resume_conflict_info_retention(), shall we rewrite the code as:

resume_conflict_info_retention(RetainDeadTuplesData *rdt_data)
{
   if (TransactionIdIsValid(MyLogicalRepWorker->oldest_nonremovable_xid))
   {
       Assert(MySubscription->retentionactive);
       reset_retention_data_fields(rdt_data);

       /* process the next phase */
        process_rdt_phase_transition(rdt_data, false);
        return;
    }

--rest of the code to start a transaction and update the catalog to
set retentionactive=true.
}

When 'MyLogicalRepWorker->oldest_nonremovable_xid' is valid, it either
means retention has not been stopped yet due to the inability to start
a txn or it is that stage of resume (subsequent calls) where catalog
has been updated and the launcher has initialized slot.xmin and
assigned it to oldest_nonremovable_xid. In both cases
'retentionactive' should be true by now and thus the Assert can be put
(as above). The dependency on 'wait_for_initial_xid' can be removed if
we do it like this.

2)
Also, I feel the code part which does txn and snapshot processing
(Start, Push, Pop, Commit, launcher-wakeup) and update catalog can be
shifted to one function and both stop_conflict_info_retention() and
resume_conflict_info_retention() can call it.

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.