Re: CREATE DATABASE with tablespace fix

Added to open items:

* fix case where template db already uses target tablespace

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Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > I am a little confused why we can't just merge the directories? The
> > relfilenodes would guarantee that the files are unique, right?
>
> Actually not: there is no uniqueness check on relfilenode beyond the
> indirect one of the files having to live in the same directory. In the
> tablespace world it will be possible for tables in different tablespaces
> to have conflicting relfilenodes. Admittedly this should be rare and
> it's probably good enough to fail only if a collision occurs --- but
> it's something that would have to be kept in mind while coding.
>
> Another issue is that since we aren't changing the template's pg_class,
> we would end up with a database in which some tables refer to the
> database's default tablespace explicitly (reltablespace = its OID) and
> some refer to it implicitly (reltablespace = 0). I'm not sure what the
> consequences of that are, but it might not be good. It would definitely
> be a state that you couldn't get into "normally". (One fairly likely
> scenario for failure is if you then try to copy this database and change
> the default TS again...)
>
> > Seems we should apply this patch
>
> I think it needs more thought. I've been busy with other issues and
> haven't expended any cycles on the problem myself ...
>
> regards, tom lane
>

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