From: Matt Mello <alien@spaceship.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-sql@postgresql.org
Subject: Re: "deadlock detected" documentation
Date: Thu, 15 May 2003 14:06:36 -0500
Message-ID: <3EC3E53C.9070800@spaceship.com> (raw)
In-Reply-To: <10286.1053018824@sss.pgh.pa.us>
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<3EC32935.5040005@spaceship.com>
<7737.1053003625@sss.pgh.pa.us>
<3EC3C239.7070708@spaceship.com>
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<3EC3C77A.3010006@spaceship.com>
<10286.1053018824@sss.pgh.pa.us>
Okay, so one last question on this...
If I do the following, assuming I haven't applied the patch, will it
still result in a deadlock (in other words, does this only happen with
multi-record updates, or can it happen with independent single-record
updates inside transactions)?
THREAD1: THREAD2:
BEGIN;
update txn set ... where txn.terminalid = 1;
BEGIN;
update txn set ... where txn.terminalid = 2;
(I anticipate the next statement will give me a deadlock.)
update txn set ... where txn.terminalid = 2;
update txn set ... where txn.terminalid = 1;
COMMIT;
COMMIT;
Thanks, again!
Tom Lane wrote:
> Matt Mello <alien@spaceship.com> writes:
>
>>I see. One item I forgot to mention ... Both update statements have a
>>where clause containing txn.terminalid=38. Txn.terminalid is a foreign
>>key column in that table (txn.terminalid->terminal.terminalid). Could
>>this be the source of the trouble?
>
>
> Not per se. The problem depends on which rows get updated and in what
> sequence --- the contents of the WHERE clause aren't the issue, except
> insofar as they determine the set of rows to be updated.
>
> regards, tom lane
>
>
--
Matt Mello
512-350-6900
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To: pgsql-sql@postgresql.org
Cc: alien@spaceship.com, tgl@sss.pgh.pa.us
Subject: Re: "deadlock detected" documentation
In-Reply-To: <3EC3E53C.9070800@spaceship.com>
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