Re: Fwd: [Bricolage-Devel] DB Deadlock Detected errors

On Mon, 7 Jul 2003, David Wheeler wrote:

> On Monday, July 7, 2003, at 09:29 AM, Stephan Szabo wrote:
>
> > Updates get write locks on the particular row involved, so if you're
> > trying something like
> > T1: update foo set a=1 where key=1;
> > T2: update bar set a=2 where key=1;
> > T1: update bar set a=3 where key=1;
> > T2: update foo set a=4 where key=1;
> > you get a deadlock I believe. It does get a shared lock on the table
> > but
> > that shouldn't affect anything.
>
> Okay, row-level locks I can handle. :-)
>
> > Another possibility would be foreign keys since those grab explicit row
> > locks on the matching rows of the other relation. It's possible that
> > Jan's patch for updates might help in that case.
>
> I'm not familiar with what's happening with PG dev. Is "Jan's patch"
> part of 7.4?

Yeah, although I believe he send a 7.3 version to -general as well. It
gets rid of locking of the associated primary key row when doing an update
on a foreign key row that doesn't change the key value.