Re: BF mamba failure

Hi,

On Thu, Nov 14, 2024 at 04:55:23PM +0900, Michael Paquier wrote:
> I've been going through this patch again, and the failures that could
> be seen because of such failures, like standbys failing in an
> unpredictible way is not cool, so I am planning to apply the attached
> down to 15 now that the release has colled down. At the end I am not
> really stressing about this addition in the structure for the sake of
> making the stats entries safe to handle.

I don't think the addition is a concern too.

> I did not like much the name "agecount" though, used to cross-check
> how many times an entry is reused in shared memory and in the local
> copy we keep in a process, so I've renamed it to "generation".

"generation" sounds more appropriate to me too.

The approach to avoid the error sounds reasonable to me.

Just 2 comments about the patch:

=== 1

Maybe use "generation" instead of generation in the comments (where it's not done,
some comments do it already).

=== 2

We could think about adding a test. That should be doable with replication slots
or custom pgstats kinds and probably injection points. But I'm not sure that's
worth it, as the code in the patch looks "simple" enough. Thoughts?

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com