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

On Thu, Sep 24, 2020 at 07:55:31PM -0500, Justin Pryzby wrote:
> This should be caught during --check, or earlier in the upgrade, rather than
> only after dumping the schema.
>
> Typically, the tablespace dir would be left behind by a previous failed upgrade
> attempt, causing a cascade of failured upgrades. I guess I may not be the only
> one with a 3 year old wrapper which has a hack to check for this.

This is an interesting failure case I never considered --- running
pg_upgrade, having it fail, deleting and recreating the _new_ cluster
directory, but not removing the new cluster's tablepace directories. I
was able to recreate the failure, and verify that your patch properly
throws an error during 'check' for this case.

Modified patch attached. I plan to apply this to all supported Postgres
versions.

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EnterpriseDB https://enterprisedb.com

The usefulness of a cup is in its emptiness, Bruce Lee