Subject: Re: Please humor me ...
From: Jeff Davis <pgsql@j-davis.com>
To: Carlos Moreno <moreno_pg@mochima.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
In-Reply-To: <461A9C86.4000008@mochima.com>
References: <461A9C86.4000008@mochima.com>
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Date: Mon, 09 Apr 2007 14:05:44 -0700
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On Mon, 2007-04-09 at 16:05 -0400, Carlos Moreno wrote:
> And by the subject, I mean:  please provide a "factual" answer, as opposed
> to the more or less obvious answer which would be "no one in their sane
> mind would even consider doing such thing"  :-)
> 
> 1) Would it be possible to entirely disable WAL?  (something like setting a
> symlink so that pg_xlog points to /dev/null, perhaps?)

You can't disable WAL, but you can disable fsync.

> 2) What would be the real implications of doing that?
> 

A good chance that you lose your entire database cluster if the power
fails.

It's not just your tables that require WAL, it's also the system
catalogs. If you were to disable it, and a system catalog became
corrupt, the database would not know what to do.

There's always a chance you could recover some of that data by a manual
process (i.e. open up the database files in a hex editor and look for
your data), but there would be no guarantee.

Regards,
	Jeff Davis