Re: Transactions involving multiple postgres foreign servers, take 2

On 2020/09/08 10:34, Amit Kapila wrote:
> On Mon, Sep 7, 2020 at 2:29 PM Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
>>
>> IMO it's not easy to commit this 2PC patch at once because it's still large
>> and complicated. So I'm thinking it's better to separate the feature into
>> several parts and commit them gradually.
>>
>
> Hmm, I don't see that we have a consensus on the design and or
> interfaces of this patch and without that proceeding for commit
> doesn't seem advisable. Here are a few points which I remember offhand
> that require more work.

Thanks!

> 1. There is a competing design proposed and being discussed in another
> thread [1] for this purpose. I think both the approaches have pros and
> cons but there doesn't seem to be any conclusion yet on which one is
> better.

I was thinking that [1] was discussing global snapshot feature for
"atomic visibility" rather than the solution like 2PC for "atomic commit".
But if another approach for "atomic commit" was also proposed at [1],
that's good. I will check that.

> 2. In this thread, we have discussed to try integrating this patch
> with some other FDWs (say MySQL, mongodb, etc.) to ensure that the
> APIs we are exposing are general enough that other FDWs can use them
> to implement 2PC. I could see some speculations about the same but no
> concrete work on the same has been done.

Yes, you're right.

> 3. In another thread [1], we have seen that the patch being discussed
> in this thread might need to re-designed if we have to use some other
> design for global-visibility than what is proposed in that thread. I
> think it is quite likely that can happen considering no one is able to
> come up with the solution to major design problems spotted in that
> patch yet.

You imply that global-visibility patch should be come first before "2PC" patch?

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION