Re: Documentation does not mention that basebackup could not be used on newer major version

On Mon, Sep 18, 2023 at 10:08:30PM +0200, Laurenz Albe wrote:
> On Mon, 2023-09-18 at 15:29 +0000, PG Doc comments form wrote:
>> My main issue is that `pg_basebackup` page does not mention that this backup
>> is compatible only with current version of database. I can not do basebackup
>> on v11 and restore that on v15, for example.
>
> I think that that is amply documented by the fact that pg_basebackup is
> *not* mentioned in https://www.postgresql.org/docs/current/upgrading.html .

Yeah. The issue with this one is that it does a direct physical copy
of the files. You cannot expect pg_basebackup to be able to do all
the work that pg_upgrade would do underground, like binary upgrades,
and more.

> You can't expect us to enumerate every tool that is not suitable for
> upgrading.

Just noting in passing. There is a lot of maintenance effort for
downward compatibility (tools like pg_dump and pg_basebackup at
version N are able to work with a backend version older, say at N-1).
Upward compabitility may work in some cases, even for dumps, still
these would likely require extra manipulation to be able to load to
a version of the backend older than the version of pg_dump used.
Being able to use pg_basebackup to work with older backend versions is
a really important property we try to keep available.
--
Michael