Re: Stack-based tracking of per-node WAL/buffer usage

On 3/14/26 21:49, Lukas Fittl wrote:
> ...
>
> Implemented this fix in IndexNext, and also expanded the tracking of
> table access to IndexNextWithReorder.
>
> Regarding Index-Only Scans, I did not add instrumentation for table
> access yet - I might add that in a follow-up revision or we could also
> do it in a follow-on patch.
>

I think we should, and it probably should be done in the same commit as
for plain index scans. Mostly for consistency / less confusion.

Every now and then there's an index-only scan that has to do a lot of
heap fetches, possibly just as many as the plain index scan. But the IOS
version would not say how many buffer accesses are for table, and users
might assume an index-only scan does not access table. Confusing.

I only started to look at the patch today, so I don't have any real
review comments. But I noticed the pg_session_buffer_usage is added only
to the contrib/meson.build and not to the Makefile. I assume that's not
intentional.

regards

--
Tomas Vondra