Re: serializable anomaly - duplicate primary keys

Hi,

> Actually I think we should do just the opposite - focus on the patch
> that can be backported and discuss possible improvements for the
> `master` branch later.

> I prepared a PoC patch that shows how this could be archived. Also it
> includes regression tests for everything discussed above.
>
> One drawback I discovered is that the patch introduces a
> false-positive conflict detection that causes the existing
> partition-key-update-3.spec to fail. I'm not 100% certain what to do
> about it. Given the fact that SSI generally has false-positives, maybe
> we should just rewrite the test? This seems to be better compared to
> what we currently have and personally I don't have better proposals at
> the moment.

I think I found a fix that doesn't break ABI or the existing
behaviour. It introduces a per-backend global variable which is not
pretty, but it works and we can always refactor the code in the
`master` branch after backpatching.

Please see PoC v2. Any feedback is most welcome.

--
Best regards,
Aleksander Alekseev