RE: Conflict detection for update_deleted in logical replication

On Tuesday, September 2, 2025 6:00 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
>
> On Mon, Sep 1, 2025 at 5:45 PM shveta malik <shveta(dot)malik(at)gmail(dot)com>
> wrote:
> >
> > >
> > > Here is V70 patch set.
> > >
> >
> > The patch v70-0001 looks good to me. Verified, all the old issues are resolved.
> >
> > Will resume review of v70-0002 now.
> >
>
> Please find a few comments on v70-0002:
>
> 1)
> - * Note: Retention won't be resumed automatically. The user must manually
> - * disable retain_dead_tuples and re-enable it after confirming that the
> - * replication slot maintained by the launcher has been dropped.
> + * The retention will resume automatically if the worker has confirmed
> + that the
> + * retention duration is now within the max_retention_duration.
>
> Do we need this comment atop stop as it does not directly concern stop? Isn't
> the details regarding RDT_RESUME_CONFLICT_INFO_RETENTION
> in the file-header section sufficient?

Agreed. I removed this comment.

>
> 2)
> + /* Stop retention if not yet */
> + if (MySubscription->retentionactive)
> + {
> + rdt_data->phase = RDT_STOP_CONFLICT_INFO_RETENTION;
>
> - /* process the next phase */
> - process_rdt_phase_transition(rdt_data, false);
> + /* process the next phase */
> + process_rdt_phase_transition(rdt_data, false); }
> +
> + reset_retention_data_fields(rdt_data);
>
> should_stop_conflict_info_retention() does reset_retention_data_fields
> everytime when wait-time exceeds the limit, and when it actually stops i.e.
> calls stop_conflict_info_retention through phase change; the stop function
> also does reset_retention_data_fields and calls process_rdt_phase_transition.
> Can we optimize this code part by consolidating the
> reset_retention_data_fields() and
> process_rdt_phase_transition() calls into
> should_stop_conflict_info_retention() itself, eliminating redundancy?

Agreed. I improved the code here.

>
> 3)
> Shall we update 035_conflicts.pl to have a resume test by setting
> max_retention_duration to 0 after stop-retention test?

Added.

>
> 4)
> + subscription. The retention will be automatically resumed
> once at least
> + one apply worker confirms that the retention duration is within the
> + specified limit, or a new subscription is created with
> + <literal>retain_dead_tuples = true</literal>, or the user manually
> + re-enables <literal>retain_dead_tuples</literal>.
>
> Shall we rephrase it slightly to:
>
> Retention will automatically resume when at least one apply worker confirms
> that the retention duration is within the specified limit, or when a new
> subscription is created with <literal>retain_dead_tuples = true</literal>.
> Alternatively, retention can be manually resumed by re-enabling
> <literal>retain_dead_tuples</literal>.

Changed as suggested.

Here is V71 patch set which addressed above comments and [1].

[1] https://www.postgresql.org/message-id/CAJpy0uC8w442wGEJ0gyR23ojAyvd-s_g-m8fUbixy0V9yOmrcg%40mail.gmail.com

Best Regards,
Hou zj