Re: DDL commands take forever

2009/12/29 Leonardo M. <l(dot)rame(at)griensu(dot)com>:
> El mar, 29-12-2009 a las 15:44 -0500, Merlin Moncure escribió:
>> right. IIRC the zeos library has a transaction mode that controls if
>> commits are explicit or invoked via the library commit method.  either
>> way, you you need to make sure that transactions are not left
>> open...this can lead (as you noticed) to unexpected problems like
>> blocking queries, performance problems, data loss, etc.
>>
>> if you notice the slow ddl issue again, throw an immediate select *
>> from pg_locks and look for granted = f.  If you find some and they
>> match your pid, then you know that you have a transaction open that is
>> blocking you.  From there, it's just a matter if using pg_locks and
>> pg_stat_activity to narrow down who/what is doing it.  You should
>> especially take note of 'idle in transaction' in
>> pg_stat_activity...this is classic red flag of leaky application code.
>>
>> merlin
>
> I did the Select * from pg_locks right after your answer, and found that
> almost all locks originated by my app have "granted = t", also, all are
> in "<IDLE> in transaction". The interesting thing is the app is doing
> only Selects, without opening transactions.

ok, the problem is clear: find out why those happened (a client issued
'begin' without subsequent 'commit') and your problem will go away.
Turn on sql logging if you have to.

merlin