Hi Christopher

>
> I see the edge case, and it's regrettably unpleasant.
>

I suppose the bottom line is that setting synchronous_commit to off in
postgresql.conf on any Slony node is inadvisable (as, in fact, setting
it to off is inadvisable in many scenarios). Luckily, it is possible
to disable it on a per-session basis, so that clients of pg databases
that are a slony-I nodes can avail themselves of asynchronous commits
where that makes sense.

Thanks,
Peter Geoghegan