From: Tom Lane <tgl@sss.pgh.pa.us>
To: Matt Mello <alien@spaceship.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: "deadlock detected" documentation
Date: Fri, 16 May 2003 15:13:48 -0400
Message-ID: <28936.1053112428@sss.pgh.pa.us> (raw)
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Matt Mello <alien@spaceship.com> writes:
> The two situations I can think of are:
> 1) Two FK fields in a single row pointing to 2 different FK tables, for
> which any 2 updates get locks in opposite order (seems like a deadlock).
I don't think this is possible, at least in 7.3. All backends are
guaranteed to run the triggers of a given table in the same order,
so the foreign-row locks should be acquired in the same column order
in all cases.
> 2) Two FK fields pointing to only 1 FK table (both fields are references
> to the same table), for which each update gets independent locks instead
> of one lock for both fields, so there is a potential that #1 problem
> could impact this as well.
Not clear what you mean by "independent locks"; there is only one row
lock on a row.
The cases that I'd be concerned about are not within-row conflicts, but
multi-row conflicts...
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, alien@spaceship.com
Subject: Re: "deadlock detected" documentation
In-Reply-To: <28936.1053112428@sss.pgh.pa.us>
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