> It looks to me like the guy doing VACUUM is simply waiting for the other
> guy to release a page-level lock. The other guy is running a deferred
> trigger and so I'd expect him to be holding one or two page-level locks,
> on the page or pages containing the tuple or tuples passed to the
> trigger. Nothing evidently wrong there.
If I remember what I was working on the other day when this whole thing
started, I think it was a single backend and a checkpoint that collided.
I'll trace that combination, assuming it happens again.
> The real question is why does vsyslog() have anything to block on, when
> it's running in an unthreaded process? Seeing that you are using
> plpython, I wonder if Python is confusing matters somehow.
Oof. I'm using plpython all over the place; I don't think this problem has
happened in any location that can work without it easily. :-/