Re: Avoiding Tablespace path collision for primary and standby

On Fri, May 25, 2018 at 7:33 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Ashwin Agrawal <aagrawal@pivotal.io> writes:
> Proposing to create directory with timestamp at time of creating tablespace
> and create symbolic link to it instead.

I'm skeptical that this solves your problem.  What happens when the CREATE
TABLESPACE command is replicated to the standby with sub-second delay?

Clock skew is another reason to doubt that timestamp == unique identifier,
which is essentially what you're assuming here.

Even if we fixed that, the general idea of including a quasi-random
component in the directory name seems like it would have a lot of
unpleasant side effects in terms of reproduceability, testability, etc.

Hmm.. aren't to some degree we currently as well create directories/files with quasi-random numbers like tablespace-oids, database-oids and relfilenodes, etc..

To generate uniqueness for the path between primary and standby need to use something which is not represented within database. So will be random to some degree. Like one can use PORT number of postmaster. As only need to generate unique path while creating link during CREATE TABLESPACE.