Re: Optimizer items in the release notes

On Sat, 27 Apr 2019 at 11:49, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>
> On Wed, Apr 24, 2019 at 02:46:15PM -0400, Adam Brusselback wrote:
> > As a user, I am interested in the optimizer changes for sure, and I
> > actually had wished they were highlighted more in previous releases.
> >
> > > I think planner smarts are arguably one of our weakest areas when
> > > compared to the big commercial databases. The more we can throw in
> > > there about this sort of thing the better.
> >
> > Completely agree on both fronts. I have run into numerous
> > optimizations I had taken for granted when I worked primarily with SQL
> > Server and were not present in Postgres. Work being done to make the
> > Postgres optimizer smarter is great, as is highlighting that work in
> > the release notes IMO.
>
> This thread highlights the challenges of having optimizer items in the
> release notes:
>
> * They often reply to only a small percentage of queries

That can often be true, but as I mentioned that it's quite common that
the queries that the changes do effect see massive performance
improvements. Some patch that gave us 5% across the board is unlikely
to unblock someone from migrating to PostgreSQL, but some query
planner smarts that reduce query times by orders of magnitude could
unblock someone.

> * They are hard to explain

That can be true, but we generally get there if not the first time
then after a few iterations. Authors and committers of the
improvements are likely to be able to help find suitable wording.

> I see the argument as wanting vague warm and fuzzy feelings that we are
> improving the optimizer, which we are.

Not sure where the warm and fuzzy argument is from. The point I tried
to make was that if we're making changes to PostgreSQL that are likely
going to be useful to people, then we likely should put them in the
release notes. It was my understanding that this was why major version
release notes were useful.

> I will see what I can do to get
> those ideas into the PG 12 release notes in as concrete a way as
> possible.

I think the current process is really good. You take on the hard task
of drafting them up, to which everyone is very grateful for as it's a
pretty tedious job. Various people that might have been closer to the
actual work done for certain items then suggest improvements.

--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services