Horton

RE: Conflict detection for update_deleted in logical replication

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

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From: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
To: shveta malik <shveta.malik@gmail.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>
Date: 2025-09-09T06:17:28Z
Lists: pgsql-hackers

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On Tuesday, September 2, 2025 6:00 PM shveta malik <shveta.malik@gmail.com> wrote:
> 
> On Mon, Sep 1, 2025 at 5:45 PM shveta malik <shveta.malik@gmail.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

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.