Re: Transactions involving multiple postgres foreign servers, take 2

On Tue, 23 Jun 2020 at 13:26, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Tue, Jun 23, 2020 at 9:03 AM Masahiko Sawada
> <masahiko(dot)sawada(at)2ndquadrant(dot)com> wrote:
> >
> >
> > I've attached the latest version patches. I've incorporated the review
> > comments I got so far and improved locking strategy.
> >
>
> Thanks for updating the patch.
>
> > Please review it.
> >
>
> I think at this stage it is important that we do some study of various
> approaches to achieve this work and come up with a comparison of the
> pros and cons of each approach (a) what this patch provides, (b) what
> is implemented in Global Snapshots patch [1], (c) if possible, what is
> implemented in Postgres-XL. I fear that if go too far in spending
> effort on this and later discovered that it can be better done via
> some other available patch/work (maybe due to a reasons like that
> approach can easily extended to provide atomic visibility or the
> design is more robust, etc.) then it can lead to a lot of rework.

Yeah, I have no objection to that plan but I think we also need to
keep in mind that (b), (c), and whatever we are thinking about global
consistency are talking about only PostgreSQL (and postgres_fdw). On
the other hand, this patch needs to implement the feature that can
resolve the atomic commit problem more generically, because the
foreign server might be using oracle_fdw, mysql_fdw, or other FDWs
connecting database systems supporting 2PC.

Regards,

--
Masahiko Sawada http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services