Re: First draft of PG 17 release notes

On Tue, May 21, 2024 at 12:27 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > I agree the impact of performance improvements are often greater than
> > the average release note item. However, if people expect Postgres to be
> > faster, is it important for them to know _why_ it is faster?
>
> Yes, it very often is.

Is it important for them to even read the release notes?

Bruce's arguments against listing performance items more often/with
greater prominence could just as easily be applied to other types of
features, in other areas. Performance is a feature (or a feature
category) -- no better or worse than any other category of feature.

> Performance improvements typically aren't "make
> everything 3% faster", they're more "make this special thing 20%
> faster". Without know what got faster, users don't know if
> a) the upgrade will improve their production situation
> b) they need to change something to take advantage of the improvement

Another important category of performance improvement is "make the
thing that was just unusable usable, for the first time ever".

Sometimes the baseline is unreasonably slow, so an improvement
effectively allows you as a user to do something that just wasn't
possible on previous versions. Other times it's addressed at something
that was very scary, like VACUUMs that need multiple rounds of index
vacuuming. Multiple rounds of index vacuuming are just woefully,
horribly inefficient, and are the single individual thing that can
make things far worse. Even if you didn't technically have that
problem before now, you did have the problem of having to worry about
it. So the work in question has sanded-down this really nasty sharp
edge. That's a substantial quality of life improvement for many users.

In short, many individual performance improvements are best thought of
as qualitative improvements, rather than quantitative improvements.

It doesn't help that there is a kind of pressure to present them as
quantitative improvements. For example, I was recently encouraged to
present my own Postgres 17 B-Tree work internally using some kind of
headline grabbing measure like "6x faster". That just seems silly to
me. I can contrive a case where it's faster by an arbitrarily large
amount. Much like how a selective index scan can be arbitrarily faster
than a sequential scan. Again, a qualitative improvement.

--
Peter Geoghegan