Re: pg_upgrade: fail early if a tablespace dir already exists for new cluster version

On Tue, Oct 20, 2020 at 09:17:22PM -0400, Tom Lane wrote:
> Justin Pryzby <pryzby@telsasoft.com> writes:
> > I wonder if pg_upgrade should try to rmdir() the tablespace dirs before
> > restoring global objects, allowing it to succeed, rather than just "failing
> > early".
> 
> I'm a little confused about that.  If the directories aren't empty,
> that will fail,

You mean rmdir() will fail, returning -1, which my patch will ignore, and the
pg_upgrade will fail, same as it would have before.  The goal of the patch is
to improve the "empty" case, only.

> but if they are, shouldn't the upgrade just work?

It fails in "Restoring global objects", which runs "CREATE TABLESPACE".
| errmsg("directory \"%s\" already in use as a tablespace",

I considered the possibility of changing that, but it seems like this is
specific to pg_upgrade.  I wouldn't want to change the core server just for
that, and it has a good reason for failing in that case:
| * The creation of the version directory prevents more than one tablespace
| * in a single location.

-- 
Justin