Re: PostgreSQL as a local in-memory cache

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Dave Page <dpage(at)pgadmin(dot)org>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Dimitri Fontaine <dfontaine(at)hi-media(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, postgres performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: PostgreSQL as a local in-memory cache
Date: 2010-06-23 20:43:06
Message-ID: 27712.1277325786@sss.pgh.pa.us
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Dave Page <dpage(at)pgadmin(dot)org> writes:
> On Wed, Jun 23, 2010 at 9:25 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> I don't think we need a system-wide setting for that. I believe that
>> the unlogged tables I'm working on will handle that case.

> Aren't they going to be truncated at startup? If the entire system is
> running without WAL, we would only need to do that in case of an
> unclean shutdown wouldn't we?

The problem with a system-wide no-WAL setting is it means you can't
trust the system catalogs after a crash. Which means you are forced to
use initdb to recover from any crash, in return for not a lot of savings
(for typical usages where there's not really much churn in the
catalogs). I tend to agree with Robert that a way to not log content
updates for individual user tables is likely to be much more useful in
practice.

regards, tom lane

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