Re: TABLESPACE and directory for Foreign tables?

Josh Berkus <josh@agliodbs.com> writes:
> On 05/05/2014 10:53 AM, Tom Lane wrote:
>> A larger and more philosophical point is that such a direction of
>> development could hardly be called a "foreign" data wrapper.  People
>> would expect Postgres to take full responsibility for such files,
>> including data integrity considerations such as fsync-at-checkpoints
>> and WAL support.  Even if we wanted the FDW abstractions to allow
>> for that, we're very far away from it.  And frankly I'd maintain
>> that FDW is the wrong abstraction.

> Certainly pluggable storage would be a better abstraction; but we don't
> have that yet.  In the meantime, we have one FDW which creates files
> *right now*, and we might have more in the future, so I'm trying to
> establish some guidelines as to how such FDWs should behave.

The guideline is simple: don't do that.  We should absolutely not
encourage this until/unless we have infrastructure to support it.
Just because one FDW author thought this would be a cool thing to do
does not make it a cool thing to do, and definitely not a cool thing
to encourage others to emulate.

> Regardless
> of whether or not you think FDWs should be managing files, it's better
> for users if all FDWs which manage files manage them in the same way.

Sure.  They should all keep them outside $PGDATA, making it not-our-
problem.  When and if we're prepared to consider it our problem, we
will be sure to advise people.
        regards, tom lane