Re: Revised Patch to allow multiple table locks in "Unison"

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Fernando Nasser <fnasser(at)redhat(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Neil Padgett <npadgett(at)redhat(dot)com>, "pgsql-patches(at)postgresql(dot)org" <pgsql-patches(at)postgresql(dot)org>, Liam Stewart <liams(at)redhat(dot)com>
Subject: Re: Revised Patch to allow multiple table locks in "Unison"
Date: 2001-07-30 17:30:29
Message-ID: 200107301730.f6UHUTJ11296@candle.pha.pa.us
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> Bruce Momjian wrote:
> >
> > The unusual case here is that deadlock is not checked on request, but
> > only after waiting on the lock for a while. This is because deadlock
> > detection is an expensive operation.
>
> But that is what happens. If one of the locks is not obtained, the
> algorithm does wait on that lock (after releasing the other locks).
> In the case of a deadlock (tom's scenario #1) it would wait forever,
> but the deadlock detection will find it in there and break it.

OK, I thought you were talking about the LOCK a,b case, not the other
case where we had a previous LOCK statement. Sorry.

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