Re: Preventing indirection for IndexPageGetOpaque for known-size page special areas

On Tue, 5 Apr 2022 at 21:45, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Fri, Apr 1, 2022 at 11:12 AM Matthias van de Meent
> <boekewurm+postgres(at)gmail(dot)com> wrote:
> > Here's a new 0001 to keep CFBot happy.
>
> This seems like it would conflict with the proposal from
> http://postgr.es/m/CA+TgmoaD8wMN6i1mmuo+4ZNeGE3Hd57ys8uV8UZm7cneqy3W2g@mail.gmail.com
> which I still hope to advance in some form at an appropriate time.

I can see why what would be the case. However, I don't think that is
of much importance here, as reverting the changes that are yet to be
committed would be trivial.

Also, I can't see why we would allow page-level layout changes in
initdb; that seems like the wrong place to do that. All page layout
currently is at compile-time; even checksums (which can be
enabled/disabled in initdb) have reserved space available in the page
header. Why would it be different for nonces?

I don't think that the 'storing an explicit nonce' patch would
conflict in any meaningful form, other than maybe needing to roll back
from PageGetSpecialOpaque to PageGetSpecialPointer when (if) the nonce
is indeed going to be stored in the special area of each page with a
size defined during initdb. Until then, we could have a nice (but
small) performance boost.

-Matthias