Marc <pgsql-general(at)mbreslow(dot)net> writes:
> Version of postgres is 8.2.4.
> ...
> second report that I always see that UPDATE statement and in the list of
> locks I see ExclusiveLock granted on the users table for one of the running
> pids but not the others.
Well, if it's not a foreign key issue then I think that the UPDATE is
blocked waiting for some previous updater of the same row to commit.
If you poke around a bit harder in pg_locks you'll probably find that
the UPDATE is waiting to acquire ShareLock on someone else's transaction
ID, and that someone else is the culprit.
regards, tom lane