Re: PostgreSQL Data Loss

From: Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM>
To: BluDes <DESPAMMAMIdarocchi(at)PERFAVOREtiscali(dot)it>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: PostgreSQL Data Loss
Date: 2007-01-26 22:00:48
Message-ID: 45BA7A10.5050700@sun.com
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If data are deleted then they are still stored in database until VACUUM
cleans them. You can look by some hex viewer, if you see some know text
data there. Or I think there is also some tool which dump tuple list
from pages.

You can also see deleted data if you change current transaction ID. But
I not sure if it is simply possible.

Before experiments, do not forget backup of database files.

Zdenek

BluDes wrote:
> Hi everyone,
> I have a problem with one of my costomers.
> I made a program that uses a PostgreSQL (win32) database to save its data.
> My customer claims that he lost lots of data reguarding his own clients
> and that those data had surely been saved on the database.
> My first guess is that he is the one who deleted the data but wants to
> blame someone else, obviously I can't prove it.
>
> Could it be possible for PostgreSQL to lose its data? Maybe with a file
> corruption? Could it be possible to restore these data?
>
> My program does not modify or delete data since its more like a log that
> only adds information. It is obviously possible to delete these logs but
> it requires to answer "yes" to 2 different warnings, so the data can't
> be deleted accidentally.
>
> I have other customers with even 10 times the amount of data of the one
> who claimed the loss but no problems with them.
> He obviously made no backups (and claims whe never told him to do them
> so we are responsible even for this) though the program has a dedicated
> Backup-section.
>
> Any suggestion?
>
> Daniele
>
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