Horton

Re: Potential G2-item cycles under serializable isolation

Tatsuo Ishii <ishii@sraoss.co.jp>

View thread View on postgr.es
From: Tatsuo Ishii <ishii@sraoss.co.jp>
To: thomas.munro@gmail.com
Cc: andres@anarazel.de, aphyr@jepsen.io, pg@bowt.ie, kgrittn@gmail.com, pgsql@j-davis.com, pgsql-bugs@lists.postgresql.org
Date: 2020-06-13T05:45:34Z
Lists: pgsql-bugs 
> On Fri, Jun 12, 2020 at 10:14 AM Thomas Munro <thomas.munro@gmail.com> wrote:
>> Here's a new attempt at that.  Attached, but I'll also just include
>> the new paragraph here because it's short:
> 
> Slightly improved version, bringing some wording into line with
> existing documentation.  s/SQL Standard/SQL standard/, and explicitly
> referring to "locking" implementations of RR and Ser (as we do already
> a few paragraphs earlier, when discussing MVCC).  My intention is to
> push this to all branches in a couple of days if there is no other
> feedback.  I propose to treat it as a defect, because I agree that
> it's weird and surprising that we don't mention SI, especially
> considering the history of the standard levels.  I mean, I guess it's
> basically implied by all the stuff that section says about MVCC vs
> traditional locking systems, and it's a super well known fact in our
> hacker community, but not using the standard term of art is a strange
> omission.
> 
> In future release perhaps we could entertain ideas like accepting the
> name SNAPSHOT ISOLATION, and writing some more use-friendly guidance,
> and possibly even reference the Generalized Isolation Level
> Definitions stuff.  I think it'd be a bad idea to stop accepting
> REPEATABLE READ and inconvenience our users, though; IMHO it's
> perfectly OK to stick with the current interpretation of the spec
> while also acknowledging flaws and newer thinking through this new
> paragraph.

+1.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

Commits

  1. Doc: Add references for SI and SSI.

  2. Improve comments for [Heap]CheckForSerializableConflictOut().

  3. Avoid update conflict out serialization anomalies.

  4. Implement genuine serializable isolation level.