Re: PostgreSQL as a local in-memory cache

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Dave Page <dpage(at)pgadmin(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, 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 20:45:09
Message-ID: 201006232045.o5NKj9304331@momjian.us
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Tom Lane wrote:
> 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

True, and in fact any postmaster crash could lead to curruption.

> 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.

OK, TODO removed.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ None of us is going to be here forever. +

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