Re: Advice on debugging what seems a deadlock with Zope and psycopg

Il giorno dom, 03/08/2008 alle 12.56 +0200, Marco Bizzarri ha scritto:
> On Sun, Aug 3, 2008 at 11:16 AM, Federico Di Gregorio <fog-NGVKUo/i/[email protected]> wrote:
> > Hi Marco,
> >
> > if I remember correctly, SELECT FOR UPDATE place a lock on the selected
> > rows so this _can_ be a deadlock problem.
> 
> Yes, SELECT FOR UPDATE do places a lock on the rows. In my testcase,
> I'm basically performing over and over (using ab) the same sequence of
> operations; they are, more or less:
> 
> SELECT FOR UPDATE to get the value of the counter
> UPDATE to increase the counter
> 
> even though there are other tables involved they should not be
> involved in this kind of problem.
> 
> And, transaction isolation level is SERIALIZABLE.
> 
> > At first sight it does not
> > seem a psycopg problem but the version you're using is so old I don't
> > remember if there were locking bugs.
> 
> Yes, I know; the version of psycopg is quite old, and I'm considering
> a migration path; the problem is that I've to consider a migration
> path for psycopg, python, Zope and PostgreSQL (altough, admitedly,
> this one seems the less probelmatic to me).
> 
> > Which version of PostgreSQL are you
> > using?
> 
> 7.4.13 (on a debian etch, if it is useful).

Mm.. you're using software that is unmaintained by ages. ;) Anyway the
only thing I can think of is lowering the transaction isolation level
and/or temporarily remove the FOR UPDATE and check what happens. If
everything goes well then it is PostgreSQL bug or a bug in your
application.

federico

-- 
Federico Di Gregorio                         http://people.initd.org/fog
Debian GNU/Linux Developer                                [email protected]
INIT.D Developer                                           fog-NGVKUo/i/[email protected]
   Abandon the search for Truth; settle for a good fantasy. -- Anonymous

_______________________________________________
Psycopg mailing list
Psycopg-IAPFreCvJWPBWskQ1e/[email protected]
http://lists.initd.org/mailman/listinfo/psycopg

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)

iEYEABECAAYFAkiV8gsACgkQvcCgrgZGjetUCACfSRB4dlV6+ZD0Wfda44RYiR4P
LRsAnRlHELKMkqAx9tJ15YKjp4UOEZ9i
=EdxF
-----END PGP SIGNATURE-----