Re: Weird problem that enormous locks

On Fri, Jul 15, 2011 at 08:22, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>wrote:

> On Thu, Jul 14, 2011 at 6:01 PM, Tony Wang <wwwjfy(at)gmail(dot)com> wrote:
> > On Fri, Jul 15, 2011 at 01:13, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>
> > wrote:
> >>
> >> On Wed, Jul 13, 2011 at 9:47 PM, Tony Wang <wwwjfy(at)gmail(dot)com> wrote:
> >> > On Thu, Jul 14, 2011 at 10:35, John R Pierce <pierce(at)hogranch(dot)com>
> >> > wrote:
> >> > It's a game server, and the queries are updating users' money, as
> >> > normal.
> >> > The sql is like "UPDATE player SET money = money + 100 where id =
> >> > 12345".
> >> > The locks were RowExclusiveLock for the table "player" and the
> indexes.
> >> > The
> >> > weird thing is there was another ExclusiveLock for the table "player",
> >> > i.e.
> >> > "player" got two locks, one RowExclusiveLock and one ExclusiveLock.
> >> > In the postgresql documentation
> >> > (http://www.postgresql.org/docs/8.4/static/explicit-locking.html)
> it's
> >> > said
> >> > about the Exclusive "This lock mode is not automatically acquired on
> >> > user
> >> > tables by any PostgreSQL command."
> >>
> >> You need to figure out what part of your app, or maybe a rogue
> >> developer etc is throwing an exclusive lock.
> >
> > Yeah, that's what I'm trying to do
>
> Cool. In your first post you said:
>
> > select pg_class.relname, pg_locks.mode, pg_locks.granted,
> pg_stat_activity.current_query, pg_stat_activity.query_start,
> > pg_stat_activity.xact_start as transaction_start,
> age(now(),pg_stat_activity.query_start) as query_age,
> > age(now(),pg_stat_activity.xact_start) as transaction_age,
> pg_stat_activity.procpid from pg_stat_activity,pg_locks left
> > outer join pg_class on (pg_locks.relation = pg_class.oid) where
> pg_locks.pid=pg_stat_activity.procpid and
> > substr(pg_class.relname,1,3) != 'pg_' order by query_start;
>
> > The only special thing I can find is that there were a lot ExclusiveLock,
> while it's normal the locks are
> > only AccessShareLock and RowExclusiveLock.
>
> So what did / does current_query say when it's happening? If it says
> you don't have access permission then run that query as root when it
> happens again.
>

As I said, it's normal update like "UPDATE player SET money = money + 100
WHERE id=12345", but there are quite many