Re: Conflict Detection and Resolution

On Thu, Jun 13, 2024 at 7:00 PM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
>
> On 2024-Jun-07, Tomas Vondra wrote:
>
> > On 6/3/24 09:30, Amit Kapila wrote:
> > > On Sat, May 25, 2024 at 2:39 AM Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> wrote:
>
> > >> How is this going to deal with the fact that commit LSN and timestamps
> > >> may not correlate perfectly? That is, commits may happen with LSN1 <
> > >> LSN2 but with T1 > T2.
>
> > But as I wrote, I'm not quite convinced this means there are not other
> > issues with this way of resolving conflicts. It's more likely a more
> > complex scenario is required.
>
> Jan Wieck approached me during pgconf.dev to reproach me of this
> problem. He also said he had some code to fix-up the commit TS
> afterwards somehow, to make the sequence monotonically increasing.
> Perhaps we should consider that, to avoid any problems caused by the
> difference between LSN order and TS order. It might be quite
> nightmarish to try to make the system work correctly without
> reasonable constraints of that nature.
>

I agree with this but the problem Jan was worried about was not
directly reproducible in what the PostgreSQL provides at least that is
what I understood then. We are also unable to think of a concrete
scenario where this is a problem but we are planning to spend more
time deriving a test to reproducible the problem.

--
With Regards,
Amit Kapila.