From: Reinoud van Leeuwen <reinoud.v@n.leeuwen.net>
To: pgsql-sql@postgresql.org
Subject: Re: [ADMIN] Deadlock on transaction
Date: Mon, 12 Feb 2007 19:59:19 +0100
Message-ID: <20070212185919.GG677@spoetnik.xs4all.nl> (raw)
In-Reply-To: <55c095e90702121008u6d3d27c0m16e52d63f97c3e7d@mail.gmail.com>
References: <55c095e90702120943v2909044eo91445b0eda3958c7@mail.gmail.com>
<1171302488.3565.15.camel@state.g2switchworks.com>
<55c095e90702121008u6d3d27c0m16e52d63f97c3e7d@mail.gmail.com>
On Mon, Feb 12, 2007 at 03:08:27PM -0300, Ezequias Rodrigues da Rocha wrote:
> I mean really deadlock. Other transactions can't access the database until
> the main transaction is complete.
What you describe sounds like a blocking lock: one transaction uses a
resource and another has to wait until it is not locked anymore
A deadlock is a special case: two transactions both need resources A and
B. transaction 1 locks A, and the next moment transaction 2 locks B. Now
transaction 1 waits for 2 to release B, but at the same time 2 waits for 1
to release A. This is called a deadlock, or circulair lock.
Postgresql automatically detects such a situation and rolls one of them
back. The client recieves a 'restartable database error' and that is
exactly true: ususally another try will work.
One method of fixing deadlocks is to make sure all your code accesses the
database in the same order. Alphabetically is easiest to remember...
--
__________________________________________________
"Nothing is as subjective as reality"
Reinoud van Leeuwen reinoud.v@n.leeuwen.net
http://www.xs4all.nl/~reinoud
__________________________________________________
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To: pgsql-sql@postgresql.org
Cc: reinoud.v@n.leeuwen.net
Subject: Re: [ADMIN] Deadlock on transaction
In-Reply-To: <20070212185919.GG677@spoetnik.xs4all.nl>
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