Re: WAL record CRC calculated incorrectly because of underlying buffer modification

On Fri, May 17, 2024 at 10:56 AM Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> I'm still not entirely clear on why hash indexes can't just follow the
> rules and exclusive lock the buffer and dirty it. Presumably
> performance would suffer, but I asked that question previously and
> didn't get an answer:
>
> https://www.postgresql.org/message-id/CA%2BTgmoY%2BdagCyrMKau7UQeQU6w4LuVEu%2ByjsmJBoXKAo6XbUUA%40mail.gmail.com

In my defense, the last time I worked on hash indexes was 7 years ago.
If this question had come up within a year or two of that work, I
probably would have both (a) had a much clearer idea of what the
answer was and (b) felt obliged to drop everything and go research it
if I didn't. But at this point, I feel like it's fair for me to tell
you what I know and leave it to you to do further research if you feel
like that's warranted. I know that we're each responsible for what we
commit, but I don't really think that should extend to having to
prioritize answering a hypothetical question ("what would happen if X
thing worked like Y instead of the way it does?") about an area I
haven't touched in long enough for every release that doesn't contain
those commits to be out of support. If you feel otherwise, let's have
that argument, but I have a feeling that it may be more that you're
hoping I have some kind of oracular powers which, in reality, I lack.

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