Re: Postgres 11 release notes

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.

Greetings,

Andres Freund