Re: Postgres 11 release notes

On Fri, May 11, 2018 at 11:50:51AM -0700, Andres Freund wrote:
> On 2018-05-11 14:44:06 -0400, Bruce Momjian wrote:
> > On Fri, May 11, 2018 at 07:49:50PM +0300, Teodor Sigaev wrote:
> > >
> > >
> > > Bruce Momjian wrote:
> > > >I have committed the first draft of the Postgres 11 release notes. I
> > > >will add more markup soon. You can view the most current version here:
> > > >
> > > > http://momjian.us/pgsql_docs/release-11.html
> > > >
> > > >I expect a torrent of feedback. ;-)
> > > Hi!
> > >
> > > Seems, you miss:
> > > 857f9c36cda520030381bd8c2af20adf0ce0e1d4 Skip full index scan during cleanup
> > > of B-tree indexes when possible
> >
> > I read that and thought it was too details to be in the release notes.
> > It is not that it is unimportant, but it is hard to see how people would
> > notice the difference or change their behavior based on this change.
>
> It's a *huge* performance problem in larger installations
> currently. When you have a multi-TB relation and correspondingly large
> relation, the VM allows to make the heap cleanups cheap, but then the
> index scan takes just about forever. I know at least one large PG user
> that moved off postgres because of it. This won't solve all of those
> concerns, but it definitely is crucial to know for such users.
>
> People would notice by vacuums of large relations not taking forever
> anymore. And the behaviour change would be to a) upgrade b) tune the
> associated reloption/GUC.

OK, so what is the text that people will understand? This?

Prevent manual VACUUMs on append-only tables from performing
needless index scans

You can see why I was hesitant to include it, based on this text, but I
am happy to add it.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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