From: Andrew Sullivan <ajs@crankycanuck.ca>
To: Joe <dev@freedomcircle.net>
Cc: Andrew Sullivan <ajs@crankycanuck.ca>
Cc: pgsql-sql@postgresql.org
Subject: Re: A long-running transaction
Date: Fri, 13 Apr 2007 13:01:08 -0400
Message-ID: <20070413170108.GD31517@phlogiston.dyndns.org> (raw)
In-Reply-To: <1176482556.782.83.camel@pampa>
References: <20070403201420.GB1519@phlogiston.dyndns.org>
<461BBE33.9030807@herakles.homelinux.org>
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<461C07A5.30000@herakles.homelinux.org>
<20070411133407.GB22510@phlogiston.dyndns.org>
<461CEF66.4010907@herakles.homelinux.org>
<20070411154923.GA22771@phlogiston.dyndns.org>
<461ED6C2.2010200@herakles.homelinux.org>
<20070413114919.GA31083@phlogiston.dyndns.org>
<1176482556.782.83.camel@pampa>
On Fri, Apr 13, 2007 at 12:42:36PM -0400, Joe wrote:
>
> Just curious: is there a way to defeat MVCC?
No. That is,
> i.e., if you can lock the
> database exclusively, there won't be any readers or writers?
while this is true, it doesn't shut off the way writes go through the
system. MVCC is rather close to the central guts of PostgreSQL.
If you want to understand more about why this is the case, what the
trade-off considerations are, &c., then I stronly advise you to troll
through the -hackers archives. Approximately once every 8-10 months
someone comes along with an idea for a change that disables MVCC in
just this or that case. Most of the time, the actual effects of this
are different than people think they will be -- concurrency is hard,
and making changes so that it's impossible to get into a race is
tricky. This is why the in-place storage management that
EnterpriseDB contributed was both somewhat controversial and somewhat
limited in its application.
A
--
Andrew Sullivan | ajs@crankycanuck.ca
This work was visionary and imaginative, and goes to show that visionary
and imaginative work need not end up well.
--Dennis Ritchie
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To: pgsql-sql@postgresql.org
Cc: ajs@crankycanuck.ca, dev@freedomcircle.net
Subject: Re: A long-running transaction
In-Reply-To: <20070413170108.GD31517@phlogiston.dyndns.org>
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