On 27.07.23 17:33, Vicențiu Ciorbaru via developers wrote:
> Rather than offer a half-truth, I would us just take a clear stance. We
> either fully support downgrading between minor versions officially
> (which has implications on how we approach bug fixes, especially on the
> storage side), or we don't even encourage it at all, stating "at your
> own risk", or do a full dump and restore as the only recovery method.
minor versions are not an issue. There were a very few cases where minor
aspects of the mysql schema changed in minor releases, but AFAIR the
last time we did that was in 10.2 days. Nowadays mysql_upgrade even
immediately returns when seeing a stored version info file from a
previous run containing the same major version number unless you use
--force.
We don't actively test this use case. If we don't test it, we can't say for certain that this is not an issue. Empirically, perhaps it works, but if we don't test, we always run the risk of not fulfilling that promise (and also not having warnings in release notes either). And this is not just about mariadb-upgrade only. If there was a forward-only change on the storage level, even if it's something that happens transparently to the end user, that also makes downgrading impossible.
Hence I would err on sticking to what we test and have the resources to manage, not say it "probably" works, or "in the past it was not an issue".
Vicentiu