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>, Masahiko Sawada <sawada.mshk@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, vignesh C <vignesh21@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, shveta malik <shveta.malik@gmail.com>
Date: 2025-09-09T09:17:20Z
Lists: pgsql-hackers 
On Tue, Sep 9, 2025 at 11:47 AM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
>
> Here is V71 patch set which addressed above comments and [1].
>

Thank You for the patches. Please find a few comments on 001:

1)
In compute_min_nonremovable_xid, when 'wait_for_xid' is true, we
should have Assert(!worker->oldest_nonremovable_xid) to ensure it is
always Invalid if reached here.

Or we can rewrite the current if-else-if code logic based on worker's
oldest-xid as main criteria as that will be NULL in both the blocks:

if (!TransactionIdIsValid(nonremovable_xid))
{
  /* resume case */
  if(wait_for_xid)
    set worker's oldest-xid using slot's xmin
  else
  /* stop case */
    return;
}

It will be slightly easier to understand.

2)
In stop_conflict_info_retention(), there may be a case where due to an
ongoing transaction, it could not update retentionactive to false. But
even in such cases, the function still sets oldest_nonremovable_xid to
Invalid, which seems wrong.

3)
Similar in resume flow, it still sets wait_for_initial_xid=true even
when it could not update retentionactive=true.

4)
resume_conflict_info_retention():
+ /*
+ * Return if the launcher has not initialized oldest_nonremovable_xid.
+ *
+ */
+ if (!TransactionIdIsValid(nonremovable_xid))
+ return;

I think we should have
'Assert(MyLogicalRepWorker->wait_for_initial_xid)' before 'return'
here.

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.