Extend documentation for pg_stat_replication.backend_xmin
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
Attachments:
0001-Extend-documentation-for-pg_stat_replication.backend.patchtext/x-patch; charset=US-ASCII; name=0001-Extend-documentation-for-pg_stat_replication.backend.patchDownload+1-1
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
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:
Show quoted text
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 replicaand 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
Attachments:
v2-0001-Extend-documentation-for-pg_stat_replication.back.patchtext/x-patch; charset=US-ASCII; name=v2-0001-Extend-documentation-for-pg_stat_replication.back.patchDownload+1-1
v2-0002-Extend-documentation-for-pg_stat_replication.back.patchtext/x-patch; charset=US-ASCII; name=v2-0002-Extend-documentation-for-pg_stat_replication.back.patchDownload+4-2
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 DaniOn 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 areplica 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