Re: Possible bugreport 8.3 beta1 on Win32: Looking like a deadlock with AutoVacuum

Alvaro Herrera schreef:
> Deblauwe Gino wrote:
>
>> OS: Windows XP Pro SP2
>> CPU: AMD Athlon 64 3500+
>> RAM: 2GB
>> DB: PostgreSQL 8.3beta1, compiled by Visual C++ build 1400
>>
>> I've come to the conclusion that it seems like a deadlock occurs when
>> dropping a column in a table the same moment that table is autovacuumed.
>>
>> Example:
>>
>> ALTER TABLE bondetail DROP COLUMN btw; (user=gino, 16252 records)
>> deadlocks with
>> VACUUM ANALYZE public.bondetail; (user=postgres)
>>
>
> Does it really deadlock, or is it just locked waiting for the vacuum to
> finish?
>
> If it deadlocks you should get a message about it and a transaction
> rollback. Otherwise you should be able to see the ungranted lock in
> pg_locks.
>
> Also it's not clear if autovacuum is involved, or you invoked the VACUUM
> ANALYZE manually. Can you clarify?
>
>
No it just looks like a deadlock on first sight. It just takes a very
long time.
In this case, it takes 10 minutes instead of 5 seconds to execute the query.

I was only able to reproduce this on 'ALTER TABLE x DROP COLUMN y;'
queries. Those things happen while upgrading
our software to a newer version. The more common instructions
(SELECT/INSERT/UPDATE/DELETE) work fine the same
as adding/changing columns/tables.

Greetings
Deblauwe Gino