Re: [PATCH] Doc: clarify that pg_upgrade statistics transfer works cross-version

On Tue, 2026-03-24 at 14:11 -0400, Bruce Momjian wrote:
> On Tue, Mar 24, 2026 at 05:53:27PM +0100, Laurenz Albe wrote:
> > Bruce, you are confusing me.  Your first sentence suggests that you
> > (erroneously) thought that upgrading statistics only works when upgrading
>
> Right.
>
> > *from* v18 or better.  But your last sentence suggests that you'd rather
> > not add anything to the documentation that could dispel that misconception.
>
> So, we don't normally document cases where a limitation does not exist.
> I think the logical place to document this is in the PG 18 release
> notes.  I am still confused why people, like myself, got this wrong.
> What is the source of the confusion?  Just unclear release notes?

I understand now, thanks.  I agree with you in principle, but I wouldn't
see that as a hard rule that should stand in the way of clarity.

Let me quote a precedent from https://www.postgresql.org/docs/current/upgrading.html

  Minor releases never change the internal storage format and are always
  compatible with earlier and later minor releases of the same major
  version number. For example, version 10.1 is compatible with version 10.0
  and version 10.6.

To me, that clarifies that there is no limitation to performing minor
updates with a simple restart.  I think that is useful information.

Perhaps you'd feel better if we phrase it as a limitation:

  Transferring optimizer statistics only work when upgrading to PostgreSQL
  version v18 or later, but there is no such limitation to the version of
  the old cluster.

I like my original suggestion better, though.

Yours,
Laurenz Albe