Tablespaces in the data directory

Someone just reported a problem when they had created a new tablespace
inside the old data directory. I'm sure there can be other issues
caused by this as well, but this is mainly a confusing scenario for
people now.

As there isn't (as far as I know at least) any actual *point* in
creating a tablespace inside the main data directory, should we
perhaps disallow this in CREATE TABLESPACE? Or at least throw a
WARNING if one does it?

--Magnus HaganderMe: http://www.hagander.net/Work: http://www.redpill-linpro.com/