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Re: deadlock_timeout at < PGC_SIGHUP?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Noah Misch <noah(at)leadboat(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: deadlock_timeout at < PGC_SIGHUP?
Date: 2011-03-29 13:20:38
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Lists: pgsql-hackers
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Tue, Mar 29, 2011 at 1:38 AM, Noah Misch <noah(at)leadboat(dot)com> wrote:
>> What is notable/surprising about the behavior when two backends have different
>> values for deadlock_timeout?

> I'd be inclined to think that PGC_SUSET is plenty.  It's actually not
> clear to me what the user could usefully do other than trying to
> preserve his transaction by setting a high deadlock_timeout - what is
> the use case, other than that?

Yeah, that was my reaction too: what is the use case for letting
different backends have different settings?  It fails to give any real
guarantees about who wins a deadlock, and I can't see any other reason
for wanting session-specific settings.

I don't know how difficult a priority setting would be.  IIRC, the
current deadlock detector always kills the process that detected the
deadlock, but I *think* that's just a random choice and not an essential
feature.  If so, it'd be pretty easy to instead kill the lowest-priority
xact among those involved in the deadlock.

			regards, tom lane

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