Re: BUG #8290: broken/unexpected locking behavior

Thank you Alvaro. Yes, this explains it.
It doesn't help to fix it but at least I know now that it's a known "feature".
I'll have to see about coming up with a work-around as we likely won't get to 9.3 anytime soon.

Thank you!

-----Original Message-----
From: pgsql-bugs-owner(at)postgresql(dot)org [mailto:pgsql-bugs-owner(at)postgresql(dot)org] On Behalf Of Alvaro Herrera
Sent: Tuesday, July 09, 2013 2:59 PM
To: pgnube(at)gmail(dot)com
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: [BUGS] BUG #8290: broken/unexpected locking behavior

pgnube(at)gmail(dot)com escribió:

> I sent the following information to pgsql-general to ask if it is
> expected locking behavior. The only responses that I got said that
> the behavior is reproducible on 9.1 and 9.3 beta 2.
> Nobody said that this is expected locking behavior and I believe it to
> be a bug, so I am filing this bug report.
> The exact steps on how to reproduce the problem are shown below.
> Thank you for putting together a great DB and for working on this bug report.

See here:
http://www.commandprompt.com/blogs/alvaro_herrera/2010/11/fixing_foreign_key_deadlocks/

There are further posts on the same topic in that blog. The patch dealing with it was finally committed for the 9.3 version, due to be released later this year:
http://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=0ac5ad5134f2769ccbaefec73844f8504c4d6182
At the bottom of the commit messages there are some message-ids on (rather long) discussions about that patch. You can search for them at http://www.postgresql.org/list/ (just enter the msgid in the box and click search).

If you try a 9.3 snapshot, you should be able to replace the FOR UPDATE in your queries with FOR NO KEY UPDATE and there should be no deadlock.
Even if it does not, I hope the aforementioned posts explain what is going on.

--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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