The following bug has been logged on the website:
Bug reference: 15582
Logged by: Andrew P
Email address: ap@zip.com.au
PostgreSQL version: 11.1
Operating system: Linux/Debian stretch
Description:
Hi,
I've added a tablespace recently to help deal with almost running out of
disk space.
I then tried to use it with:
ALTER TABLE schema.table SET TABLESPACE hydro2_tmp;
This worked in so far as disk space was used on hydro2_tmp but nothing was
ever freed in the default location.
I tried a VACUUM FULL but that did not help.
Then I tried moving the indexes belonging to the table but that also did not
help.
Everywhere I've read and everyone I spoke to said that this is a move
operation but it appears to be a copy so, unless I missed something, this
appears to be a bug.
The two table spaces are on separate drives and postgres is from postgres'
apt repository.