Re: Transactions involving multiple postgres foreign servers, take 2

On Tue, May 19, 2020 at 12:33 PM Masahiko Sawada
<masahiko(dot)sawada(at)2ndquadrant(dot)com> wrote:
>
> I think that the current three values are useful for users. The
> ‘required’ mode is used when users want to ensure all writes involved
> with the transaction are committed atomically. That being said, as
> some FDW plugin might not support the prepare API we cannot force
> users to use this mode all the time when using atomic commit.
> Therefore ‘prefer’ mode would be useful for this case. Both modes use
> 2pc only when it's required for atomic commit.
>
> So what do you think my idea that adding the behavior you proposed as
> another new mode? As it’s better to keep the first version simple as
> much as possible
>

If the intention is to keep the first version simple, then why do we
want to support any mode other than 'required'? I think it will limit
its usage for the cases where 2PC can be used only when all FDWs
involved support Prepare API but if that helps to keep the design and
patch simpler then why not just do that for the first version and then
extend it later. OTOH, if you think it will be really useful to keep
other modes, then also we could try to keep those in separate patches
to facilitate the review and discussion of the core feature.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com