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?
I thought timestamps have micro-second precision. Are we expecting tabelspace to be created, wal logged, streamed, and replayed on mirror in micro-second ?
Clock skew is another reason to doubt that timestamp == unique identifier, which is essentially what you're assuming here.
On same machine is what we care about generating uniqueness. Different machines the problem doesn't exist anyways, so doesn't matter clock is skewed or not.
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.
