Horton

Re: snapbuild woes

Andres Freund <andres@anarazel.de>

View thread View on postgr.es
From: Andres Freund <andres@anarazel.de>
To: Noah Misch <noah@leadboat.com>
Cc: pgsql-hackers@postgresql.org, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Erik Rijkers <er@xs4all.nl>, David Steele <david@pgmasters.net>, Petr Jelinek <petr.jelinek@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, Craig Ringer <craig@2ndquadrant.com>, pgsql-hackers-owner@postgresql.org
Date: 2017-05-12T01:31:27Z
Lists: pgsql-hackers

Attachments

On 2017-05-11 14:54:26 -0700, Andres Freund wrote:
> On 2017-05-11 14:51:55 -0700,  wrote:
> > On 2017-05-08 00:10:12 -0700, Andres Freund wrote:
> > > I plan to commit the next pending patch after the back branch releases
> > > are cut - it's an invasive fix and the issue doesn't cause corruption
> > > "just" slow slot creation. So it seems better to wait for a few days,
> > > rather than hurry it into the release.
> > 
> > Now that that's done, here's an updated version of that patch.  Note the
> > new logic to trigger xl_running_xact's to be logged at the right spot.
> > Works well in my testing.
> > 
> > I plan to commit this fairly soon, unless somebody wants a bit more time
> > to look into it.
> > 
> > Unless somebody protests, I'd like to slightly revise how the on-disk
> > snapshots are stored on master - given the issues this bug/commit showed
> > with the current method - but I can see one could argue that that should
> > rather be done next release.
> 
> As usual I forgot my attachement.

This patch also seems to offer a way to do your 0005 in, possibly, more
efficient manner.  We don't ever need to assume a transaction is
timetravelling anymore.  Could you check whether the attached, hasty,
patch resolves the performance problems you measured?  Also, do you have
a "reference" workload for that?

Regards,

Andres

Commits

  1. Fix thinko introduced in 2bef06d516460 et al.

  2. Avoid superfluous work for commits during logical slot creation.

  3. Fix race condition leading to hanging logical slot creation.

  4. Don't use on-disk snapshots for exported logical decoding snapshot.

  5. Preserve required !catalog tuples while computing initial decoding snapshot.