Horton

Re: snapbuild woes

Petr Jelinek <petr.jelinek@2ndquadrant.com>

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From: Petr Jelinek <petr.jelinek@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>, Noah Misch <noah@leadboat.com>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Erik Rijkers <er@xs4all.nl>, David Steele <david@pgmasters.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Robert Haas <robertmhaas@gmail.com>, Craig Ringer <craig@2ndquadrant.com>, pgsql-hackers-owner@postgresql.org
Date: 2017-04-20T11:32:10Z
Lists: pgsql-hackers 
On 20/04/17 02:09, Andres Freund wrote:
> On 2017-04-17 21:16:57 -0700, Andres Freund wrote:
>> I think we might need some more tests for this to be committable, so
>> it might not become committable tomorrow.
> 
> I'm working on some infrastructure around this.  Not sure if it needs to
> be committed, but it's certainly useful for evaluation.  Basically it's
> a small UDF that:
> 1) creates a slot via walsender protocol (to some dsn)
> 2) imports that snapshot into yet another connection to that dsn
> 3) runs some query over that new connection
> 
> That makes it reasonably easy to run e.g. pgbench and continually create
> slots, and use the snapshot to run queries "verifying" that things look
> good.  It's a bit shoestring-ed together, but everything else seems to
> require more code. And it's just test.
> 
> Unless somebody has a better idea?
> 

I don't. I mean it would be nice to have isolation tester support
walsender protocol, but I don't know anything about isolation tester
internals so no idea how much work that is. On top of that some of the
issues are not even possible to provoke via isolation tester (or
anything similar that would give us control over timing) unless we
expose a lot of guts of xlog/xact as a UDFs as well. So I think simple
function that does what you said and pgbench are reasonable solutions. I
guess you plan to make that as one of the test/modules or something
similar (the UDF)?

-- 
  Petr Jelinek                  http://www.2ndQuadrant.com/
  PostgreSQL Development, 24x7 Support, Training & Services

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.