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Re: SKIP LOCKED DATA (work in progress) - Mailing list pgsql-hackers

From Alvaro Herrera
Subject Re: SKIP LOCKED DATA (work in progress)
Date
Msg-id 20140827161845.GF7046@eldon.alvh.no-ip.org
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In response to Re: SKIP LOCKED DATA (work in progress)  (Thomas Munro <munro@ip9.org>)
Responses Re: SKIP LOCKED DATA (work in progress)
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Thomas Munro wrote:
> On 25 August 2014 02:57, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
> > Thomas Munro wrote:
> >> The difficulty of course will be testing all these racy cases reproducibly...
> >
> > Does this help?
> > http://www.postgresql.org/message-id/51FB4305.3070600@2ndquadrant.com
> > The useful trick there is forcing a query to get its snapshot and then
> > go to sleep before actually doing anything, by way of an advisory lock.
> 
> Yes it does, thanks Alvaro and Craig.  I think the attached spec
> reproduces the problem using that trick, ie shows NOWAIT blocking,
> presumably in EvalPlanQualFetch (though I haven't stepped through it
> with a debugger yet).  I'm afraid I'm out of Postgres hacking cycles
> for a few days, but next weekend I should have a new patch that fixes
> this by teaching EvalPlanQualFetch about wait policies, with isolation
> tests for NOWAIT and SKIP LOCKED.

Hmm, http://www.postgresql.org/message-id/51FB6703.9090801@2ndquadrant.com


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

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