Subject: Re: Improve documentation for pg_upgrade, standbys and rsync

From: Robert Haas <[email-masked]>
Date: Tue, 5 Apr 2022 12:38:04 -0400

On Mon, Jul 26, 2021 at 3:11 PM Stephen Frost <[email-masked]> wrote:
> * Laurenz Albe ([email-masked]) wrote:
> > Thanks for looking at this!
>
> Sure.  Thanks for working on it!

Stephen, do you intend to do something about this patch in terms of
getting it committed? You're the only reviewer but haven't responded
to the thread for more than 5 months.

I don't feel that I know this area of the documentation well enough to
feel comfortable passing judgement on whether this change is an
improvement or not. However I do feel somewhat uncomfortable with
this:

-   <step>
-    <title>Prepare for standby server upgrades</title>
-
-    <para>
-     If you are upgrading standby servers using methods outlined in
section <xref
-     linkend="pgupgrade-step-replicas"/>, verify that the old standby
-     servers are caught up by running <application>pg_controldata</application>
-     against the old primary and standby clusters.  Verify that the
-     <quote>Latest checkpoint location</quote> values match in all clusters.
-     (There will be a mismatch if old standby servers were shut down
-     before the old primary or if the old standby servers are still running.)
-     Also, make sure <varname>wal_level</varname> is not set to
-     <literal>minimal</literal> in the
<filename>postgresql.conf</filename> file on the
-     new primary cluster.
-    </para>
-   </step>

Right now, we say that you should stop the standby servers and then
prepared for standby server upgrades. With this patch, we say that you
should first prepare for standby server upgrades, and then stop the
standby servers. But the last part of the text about preparing for
standby server upgrades now mentions things to be done after carrying
out the next step where the servers are actually stopped. That seems
confusing. Perhaps we need two separate steps here, one to be
performed before stopping both servers and the other after.

Also, let me express my general terror at the idea of anyone actually
using this procedure.

Regards,

-- 
Robert Haas
EDB: http://www.enterprisedb.com