Subject: Re: Recover rows deleted
From: Jeff Davis <pgsql@j-davis.com>
To: Alejandro Carrillo <fasterzip@yahoo.es>
Cc: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
In-Reply-To: <1338229453.91030.YahooMailNeo@web171005.mail.ukl.yahoo.com>
References: <1338229453.91030.YahooMailNeo@web171005.mail.ukl.yahoo.com>
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Date: Tue, 29 May 2012 13:53:20 -0700
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On Mon, 2012-05-28 at 19:24 +0100, Alejandro Carrillo wrote:
> Hi,
> 
> 
> ¿How I can recover a row delete of a table that wasn't vacuummed?
> I have PostgreSQL 9.1 in Windows XP/7.

The first thing to do is shut down postgresql and take a full backup of
the data directory, including any archived WAL you might have (files in
pg_xlog). Make sure this is done first.

Next, do you have any backups? If you have a base backup from before the
delete, and all the WAL files from the time of the base backup until
now, then you can try point-in-time recovery to the point right before
the data loss:

http://www.postgresql.org/docs/9.1/static/continuous-archiving.html

If not, are we talking about a single row, or many rows? If it's a
single row you might be able to do some manual steps, like examining the
pages to recover the data.

Another option is to try pg_resetxlog (make sure you have a safe backup
first!):

http://www.postgresql.org/docs/9.1/static/app-pgresetxlog.html

And try setting the current transaction ID to just before the delete
ran. Then you may be able to use pg_dump or otherwise export the deleted
rows.

Regards,
	Jeff Davis