Re: Avoiding Tablespace path collision for primary and standby

On Wed, Jun 20, 2018 at 9:39 AM Bruce Momjian <bruce(at)momjian(dot)us> wrote:

> On Fri, May 25, 2018 at 02:17:23PM -0700, Ashwin Agrawal wrote:
> >
> > On Fri, May 25, 2018 at 7:33 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >
> > Ashwin Agrawal <aagrawal(at)pivotal(dot)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 ?
>
> I didn't see anyone answer your question above. We don't expect
> micro-second replay, but clock skew, which Tom Lane mention, could make
> it appear to be a micro-second replay.
>

Thanks Bruce for answering. Though I still don't see why clock skew is a
problem here. As I think clock skew only happens across machines. On same
machine why would it be an issue. Problem is only with same machine,
different machines anyways paths don't collide so even if clock skew
happens is not a problem. (I understand there may be reservations for
putting timestamp in directory path, but clock skew argument is not clear.)