I wrote:
> It'd be nice if it were as simple as that, but my experiments say that
> it isn't.
It took me a little bit to dig up the results of my previous
experiments, but here they are:
http://archives.postgresql.org/pgsql-hackers/2005-10/msg00684.php
AFAICT, setting all vs some of the variables isn't a factor; at least
not in 10.4 (couldn't say about 10.3 anymore).
regards, tom lane