Date: Mon, 19 Nov 2012 13:12:25 +0100
From: Andres Freund <andres@2ndquadrant.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: foreign key locks
Message-ID: <20121119121225.GB28067@awork2.anarazel.de>
References: <4FEAB90A0200002500048B7D@gw.wicourts.gov>
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	<20121018195820.GO3763@alvh.no-ip.org>
	<201210270006.54728.andres@2ndquadrant.com>
	<20121114152347.GA5161@alvh.no-ip.org>
	<20121114162726.GE5161@alvh.no-ip.org>
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On 2012-11-14 13:27:26 -0300, Alvaro Herrera wrote:
> Alvaro Herrera wrote:
>
> > > * In heap_lock_tuple's  XMAX_IS_MULTI case
> > >
> > > [snip]
> > >
> > > why is it membermode > mode and not membermode >= mode?
> >
> > Uh, that's a bug.  Fixed.  As noticed in the comment above that snippet,
> > there was a deadlock possible here.  Maybe I should add a test to ensure
> > this doesn't happen.
>
> Done:
> https://github.com/alvherre/postgres/commit/df2847e38198e99f57e52490e1e9391ebb70d770
>
> (I don't think this is worth a v24 submission).

One more observation:
        /*
         * Get and lock the updated version of the row; if fail, return
        NULL.
         */
-       copyTuple = EvalPlanQualFetch(estate, relation, LockTupleExclusive,
+       copyTuple = EvalPlanQualFetch(estate, relation, LockTupleNoKeyExclusive,

That doesn't seem to be correct to me. Why is it ok to acquire a
potentially too low locklevel here?

Greetings,

Andres Freund

--
 Andres Freund	                   http://www.2ndQuadrant.com/
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