Re: 2PC-induced lockup

From: Hans-Juergen Schoenig <postgres(at)cybertec(dot)at>
To: Peter Eisentraut <peter_e(at)gmx(dot)net>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: 2PC-induced lockup
Date: 2007-07-10 13:21:07
Message-ID: E4E8FDC4-FF7F-4B89-BE8B-80780A263FB5@cybertec.at
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is it good to allow locks on system tables at all?
i am not so sure. have seen some disaster in the past with that. just
consider somebody placing ACCESS EXCLUSIVE LOCK on a system table. it
is basically denial of service.

best regards,

hans

On Jul 10, 2007, at 3:14 PM, Peter Eisentraut wrote:

> The following command sequence appears to lock up the database system:
>
> BEGIN;
> LOCK pg_authid;
> PREPARE TRANSACTION 'foo';
> \q
>
> After that you can't connect anymore, even in single-user mode.
> The only way
> I could find is to clear out the pg_twophase directory, but I'm not
> sure
> whether it is safe to do that.
>
> Should this be prevented somehow, and is there a better recovery path?
>
> --
> Peter Eisentraut
> http://developer.postgresql.org/~petere/
>
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> TIP 5: don't forget to increase your free space map settings

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