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  1. doc: Clarify when backend_xmin in pg_stat_replication can be NULL.

  1. Extend documentation for pg_stat_replication.backend_xmin

    Renzo Dani <arons7@gmail.com> — 2025-10-15T15:47:33Z

    Hi,
recently I had some issue understanding what was going on with a replica
and the reported xmin.
I have than created a patch to better specify the value expected into
the pg_stat_replication.backend_xmin field.

Regards,
Renzo Dani

  2. Re: Extend documentation for pg_stat_replication.backend_xmin

    Fujii Masao <masao.fujii@gmail.com> — 2025-10-16T03:31:57Z

    On Thu, Oct 16, 2025 at 12:47 AM Renzo Dani <arons7@gmail.com> wrote:
>
> Hi,
> recently I had some issue understanding what was going on with a replica and the reported xmin.
> I have than created a patch to better specify the value expected into the pg_stat_replication.backend_xmin field.

+1

+       This field will be null if a replication slot is used; in that
case, the xmin is available through <link
linkend="view-pg-replication-slots">pg_replication_slots</link>.

I think it would be better to also mention that this field is null
when hot_standby_feedback is disabled.

Also, <literal> tags should be used for "xmin", and a newline should
be added to avoid an overly long line.

Based on the above comments, how about revising it as follows?

+       This field will be null if a replication slot is used (in this case,
+       the standby's <literal>xmin</literal> is shown in
+       <link linkend="view-pg-replication-slots">pg_replication_slots</link>)
+       or if <varname>hot_standby_feedback</varname> is disabled.

Regards,

-- 
Fujii Masao

  3. Re: Extend documentation for pg_stat_replication.backend_xmin

    Renzo Dani <arons7@gmail.com> — 2025-10-16T06:07:42Z

    Really nice,
Thanks a lot for the info and review.
Taken into the patch.

Regards,
Renzo Dani

On Thu, Oct 16, 2025 at 5:32 AM Fujii Masao <masao.fujii@gmail.com> wrote:

> On Thu, Oct 16, 2025 at 12:47 AM Renzo Dani <arons7@gmail.com> wrote:
> >
> > Hi,
> > recently I had some issue understanding what was going on with a replica
> and the reported xmin.
> > I have than created a patch to better specify the value expected into
> the pg_stat_replication.backend_xmin field.
>
> +1
>
> +       This field will be null if a replication slot is used; in that
> case, the xmin is available through <link
> linkend="view-pg-replication-slots">pg_replication_slots</link>.
>
> I think it would be better to also mention that this field is null
> when hot_standby_feedback is disabled.
>
> Also, <literal> tags should be used for "xmin", and a newline should
> be added to avoid an overly long line.
>
> Based on the above comments, how about revising it as follows?
>
> +       This field will be null if a replication slot is used (in this
> case,
> +       the standby's <literal>xmin</literal> is shown in
> +       <link
> linkend="view-pg-replication-slots">pg_replication_slots</link>)
> +       or if <varname>hot_standby_feedback</varname> is disabled.
>
> Regards,
>
> --
> Fujii Masao
>

  4. Re: Extend documentation for pg_stat_replication.backend_xmin

    Renzo Dani <arons7@gmail.com> — 2025-10-16T06:28:29Z

    On Thu, Oct 16, 2025 at 8:07 AM Renzo Dani <arons7@gmail.com> wrote:

> Really nice,
> Thanks a lot for the info and review.
> Taken into the patch.
>
> Regards,
> Renzo Dani
>
> On Thu, Oct 16, 2025 at 5:32 AM Fujii Masao <masao.fujii@gmail.com> wrote:
>
>> On Thu, Oct 16, 2025 at 12:47 AM Renzo Dani <arons7@gmail.com> wrote:
>> >
>> > Hi,
>> > recently I had some issue understanding what was going on with a
>> replica and the reported xmin.
>> > I have than created a patch to better specify the value expected into
>> the pg_stat_replication.backend_xmin field.
>>
>> +1
>>
>> +       This field will be null if a replication slot is used; in that
>> case, the xmin is available through <link
>> linkend="view-pg-replication-slots">pg_replication_slots</link>.
>>
>> I think it would be better to also mention that this field is null
>> when hot_standby_feedback is disabled.
>>
>> Also, <literal> tags should be used for "xmin", and a newline should
>> be added to avoid an overly long line.
>>
>> Based on the above comments, how about revising it as follows?
>>
>> +       This field will be null if a replication slot is used (in this
>> case,
>> +       the standby's <literal>xmin</literal> is shown in
>> +       <link
>> linkend="view-pg-replication-slots">pg_replication_slots</link>)
>> +       or if <varname>hot_standby_feedback</varname> is disabled.
>>
>> Regards,
>>
>> --
>> Fujii Masao
>>
>
I think I did it the wrong way with the patches.
So here again with all in one file.
Sorry for that.

Regards
Renzo

  5. Re: Extend documentation for pg_stat_replication.backend_xmin

    Fujii Masao <masao.fujii@gmail.com> — 2025-10-17T05:06:02Z

    On Thu, Oct 16, 2025 at 3:28 PM Renzo Dani <arons7@gmail.com> wrote:
> I think I did it the wrong way with the patches.
> So here again with all in one file.

Thanks for updating the patch! I've pushed the patch.

Regards,

-- 
Fujii Masao