Re: Tracking down deadlocks

Thanks for the quick reply (and summary!).

According to the messages I've found on the list, basically the answer
seems to be, "don't do this." On the other hand, pretty much every
message on the subject is pre-7.4. There is some mention of using
deferred foreign keys to reduce the chance for a deadlock, but nothing
says doing that actually eliminates the chance.

Is this just a known limitation? In this particular instance, I
probably could get rid of my foreign keys and if things go bad it
wouldn't hurt anything.... but I make heavy use of foreign keys
throughout the rest of my schema, which are useful for the programs
that aren't doing data mining. I wouldn't want to get rid of those
foreign keys.

On Jun 16, 2004, at 8:54 AM, Csaba Nagy wrote:

> Hi Ben,
>
> Check this mailing list for "foreign keys" and "deadlock".
> Short info:
> Postgres exclusively locks the referenced records of a foreign key
> relationship when the child record is updated, so multiple runs (in
> different transactions) of one insert query could cause deadlock if
> they
> update rows which reference the same parent keys in reverse order.
> Check your foreign keys...
>
> HTH,
> Csaba.
>
> On Wed, 2004-06-16 at 17:33, Ben wrote:
>> I'm doing a bunch of data mining against a postgres database and have
>> run into an interesting problem with deadlocks. The problem is,
>> postgres is detecting them and then wacking the offending process, and
>> I can't figure out what's causing them. I have a ton of select queries
>> (but none for update), and then a single query to insert into a table.
>> Nothing selects from that table. So where could the deadlock be?
>>
>> pg_stat_activity has a column named current_query, which would seem
>> useful in tracking this down, but it's not being populated.
>>
>> Oh, I'm running 7.4.2.
>>
>>
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