Re: Improving connection scalability: GetSnapshotData()

On Tue, 15 Sep 2020 at 07:17, Andres Freund <andres@anarazel.de> wrote:
>
> Hi,
>
> On 2020-09-09 17:02:58 +0900, Ian Barwick wrote:
> > Attached, though bear in mind I'm not very familiar with parts of this,
> > particularly 2PC stuff, so consider it educated guesswork.
>
> Thanks for this, and the test case!
>
> Your commit fixes the issues, but not quite correctly. Multixacts
> shouldn't matter, so we don't need to do anything there. And for the
> increases, I think they should be inside the already existing
> ProcArrayLock acquisition, as in the attached.
>
>
> I've also included a quite heavily revised version of your test. Instead
> of using dblink I went for having a long-running psql that I feed over
> stdin. The main reason for not liking the previous version is that it
> seems fragile, with the sleep and everything.  I expanded it to cover
> 2PC is as well.
>
> The test probably needs a bit of cleanup, wrapping some of the
> redundancy around the pump_until calls.
>
> I think the approach of having a long running psql session is really
> useful, and probably would speed up some tests. Does anybody have a good
> idea for how to best, and without undue effort, to integrate this into
> PostgresNode.pm?  I don't really have a great idea, so I think I'd leave
> it with a local helper in the new test?

2ndQ has some infra for that and various other TAP enhancements that
I'd like to try to upstream. I'll ask what I can share and how.

-- 
 Craig Ringer                   http://www.2ndQuadrant.com/
 2ndQuadrant - PostgreSQL Solutions for the Enterprise