On Wed, May 23, 2018 at 09:36:33AM -0400, Tom Lane wrote:
> Offhand, I think we do not support tablespaces that are physically inside
> the data directory, either.
pg_upgrade and pg_basebackup work funnily in such cases.
> I think there's been some discussion of having CREATE TABLESPACE try to
> detect and reject such cases. But it would be easy enough to fool it
> (through symlinks, variant path spellings, etc), that people haven't been
> excited about adding such a check.
33cb8ff6 has added a warning when doing this operation. Here is the
related thread:
https://www.postgresql.org/message-id/CA%2BTgmobZLyLU8tFCbMqbjMWB6t%2B%3DERaDo820uQEJCVAQK_Paow%40mail.gmail.com
--
Michael