Re: often PREPARE can generate high load (and sometimes minutes long unavailability)

2014-02-23 21:32 GMT+01:00 Andres Freund <andres(at)2ndquadrant(dot)com>:

> Hi,
>
> On 2014-02-23 20:04:39 +0100, Pavel Stehule wrote:
> > There is relative few very long ProcArrayLocks lwlocks
> >
> > This issue is very pathologic on fast computers with more than 8 CPU.
> This
> > issue was detected after migration from 8.4 to 9.2. (but tested with same
> > result on 9.0) I see it on devel 9.4 today actualized.
> >
> > When I moved PREPARE from cycle, then described issues is gone. But when
> I
> > use a EXECUTE IMMEDIATELY, then the issue is back. So it looks it is
> > related to planner, ...
>
> In addition to the issue Jeff mentioned, I'd suggest trying the same
> workload with repeatable read. That can do *wonders* because of the
> reduced number of snapshots.
>
>
I tested it, and it doesn't help.

Is there some patch, that I can test related to this issue?

> Greetings,
>
> Andres Freund
>
> --
> Andres Freund http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Training & Services
>