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: 2025-08-25T11:03:31Z
Lists: pgsql-hackers 
On Mon, Aug 25, 2025 at 12:09 PM shveta malik <shveta.malik@gmail.com> wrote:
>
> 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):
>

All previously reported bugs seem to be fixed on the latest patch.

Please find a few comments on v65 though:

1)

 The comment atop adjust_xid_advance_interval() says:
~~
* The interval is reset to the lesser of 100ms and
* max_conflict_retention_duration once there is some activities on the node.
~~

 But we are not doing min of the 2 values when we find new-xid (i.e.
we see activity on node)

                /*
                 * A new transaction ID was found or the interval is not yet
                 * initialized, so set the interval to the minimum value.
                 */
                rdt_data->xid_advance_interval = MIN_XID_ADVANCE_INTERVAL;

2)
* max_conflict_retention_duration once there is some activities on the node.

activities-->activity

3)
On putting some logs, when all subs stopped retention, the values are:

LOG:  ***** can_advance_xmin:1, retention_inactive:0, xmin:0
LOG:  ***** can_advance_xmin:1, retention_inactive:0, xmin:0

can_advance_xmin:1 and xmin=0 seems contradictory. Can we do something
here to improve this situation?

4)
Also I fail to think of a scenario where retention_inactive will be
useful as everything seems to be handled using can_advance_xmin
already i.e. slot is updated to have invalid xmin only through
'can_advance_xmin' without relying on retention_inactive.

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.