| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Bill Moseley <moseley(at)hank(dot)org> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Tracking down a deadlock |
| Date: | 2009-05-04 01:08:29 |
| Message-ID: | 6605.1241399309@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Bill Moseley <moseley(at)hank(dot)org> writes:
> Then when I run the test script (which runs the same transaction in two
> processes at the same time) and get a deadlock the same query is shown twice
> both with "waiting" set true:
> UPDATE account set foo = 123 where id = $1
> And if I remove that update from the transaction I no longer have the deadlock.
> So, it seems like that is the problem update.
> Is postgresql telling me that it's deadlocked on two transactions trying to run
> that same update?
Looks like it.
> There are no other updates to that account table in the transaction, so I'm
> confused how that is causing a deadlock.
Is there more than one row with the target id? Does the account table
have any foreign-key references to or from it? It's sometimes possible
to get a deadlock associated with trying to lock FK-referenced rows that
several updated rows have in common.
regards, tom lane
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