Re: Add a GUC check hook to ensure summarize_wal cannot be enabled when wal_level is minimal

On Wed, Jul 10, 2024 at 1:56 AM Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
> I believe this issue occurs when the server is shut down cleanly.
> The shutdown-checkpoint record retains the wal_level value used
> before the shutdown. If wal_level is changed after this,
> the wal_level that indicated by the shutdown-checkpoint record
> and that the WAL data generated afterwards depends on may not match.

Oh, that's a problem. I'll have to think about that.

> I'm sure this patch is necessary as a safeguard for WAL summarization.
> OTOH, I also think we should apply the patch I proposed earlier
> in this thread, which prevents summarize_wal from being enabled
> when wal_level is set to minimal. This way, if there's
> a misconfiguration, users will see an error message and
> can quickly identify and fix the issue. Thought?

I interpreted these emails as meaning that we should not proceed with
that approach:

https://www.postgresql.org/message-id/CAGECzQR2r-rHFLQr5AonFehVP8DiFH+==R2yqdBvunYnwxsXNA@mail.gmail.com
http://postgr.es/m/3253790.1720019802@sss.pgh.pa.us

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