Hi Maksim,

Do you mean MVCC will not work at all or MVCC will not support indices
after your changes?
Anyway, this looks like a major change and may be too harmful for the minor
version (10.1).

Before break MVCC index (or MVCC mode) we should force the user first to
drop all MVCC indices (or even MVCC caches) before switching to the version
with a fix.
The migration process should be well-documented as well.

I believe a user should be able to migrate to the new Ignite version with
exited persistence with no issues. E.g.
* Ignite shouldn't start if existed persistence has a MVCC index (cache)
and maybe other internal persistent MVCC structures.
* Even if the user dropped all MVCC indices/caches before the upgrade,
probably there can be an incomplete checkpoint and there are WAL records
related to MVCC in WAL that should be correctly processed.




On Thu, Mar 25, 2021 at 1:27 PM Maksim Timonin <timonin.ma...@gmail.com>
wrote:

> Hi, Igniters!
>
> the MVCC feature marked as IgniteExperimental and this annotation is more
> weaker than deprecated. So we can remove this functionality in any moment.
> So I propose:
> 1. Now I leave all affected tests marked as ignored.
> 2. Create a ticket for removing TRANSACTIONAL_SNAPSHOT from
> CacheAtomicityMode for a future minor release 10.1.
> 3. There is a ticket for removing all MVCC code [1]. So we can finish it in
> any release for future.
>
> [1] https://issues.apache.org/jira/browse/IGNITE-13871
>
> WDYT?
>
>
> On Mon, Mar 15, 2021 at 9:58 PM Maksim Timonin <timonin.ma...@gmail.com>
> wrote:
>
> > Hi, Igniters!
> >
> > I'm working on a feature (moving indexes to the core module) and skip
> > specific implementation for MVCC as it is considered deprecated (the vote
> > result [1]). Am I right that now there is no need to support MVCC? Then
> > there are a lot of tests (both Java, C++) that fail because they run with
> > TRANSACTIONAL_SNAPSHOT atomicity mode.
> >
> > There are 2 cases:
> > 1. MVCC mode is just a parameter of a test. I just removed it from a
> > parameters list;
> > 2. There are tests that run only for MVCC. I marked them with the @Ignore
> > annotation.
> >
> > But would it better just completely remove all such tests that are broken
> > by the patch?
> >
> > [1]
> >
> http://apache-ignite-developers.2346864.n4.nabble.com/RESULT-VOTE-Removing-MVCC-public-API-td50705.html#a50706
> >
>


-- 
Best regards,
Andrey V. Mashenkov

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