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From Dmitriy Setrakyan <dsetrak...@apache.org>
Subject Re: snapshot transaction isolation
Date Thu, 04 Feb 2016 09:31:30 GMT
I think the whole point is to lock 1st and get 2nd. If you do a getAll,
isn’t it possible that some value will be updated before you get it? If
yes, then user’s logic will potentially be based on a wrong value, no?

D.

On Thu, Feb 4, 2016 at 1:29 AM, Alexey Goncharuk <alexey.goncharuk@gmail.com
> wrote:

> If all keys are known in advance, how is it different from starting a
> pessimistic transaction and invoking getAll() on those keys? Introducing a
> new concept with such restrictions does not makes sense to me.
>
> 2016-02-04 1:27 GMT+03:00 Dmitriy Setrakyan <dsetrakyan@apache.org>:
>
> > Igniters,
> >
> > I keep hearing questions from users about the snapshot isolation.
> Currently
> > ignite provides Optimistic and Pessimistic
> > <
> >
> https://apacheignite.readme.io/docs/transactions#optimistic-and-pessimistic
> > >
> > transactions [1]. This modes ensure that transactional values are
> > consistent with each other on 1st access of each value.
> >
> > However, some use cases require that transactional values are consistent
> > with each other not at 1st access, but at transaction start time. After
> > giving it some thought, I think we can support it with minimal effort, if
> > we add a few restrictions. For example, we can easily support it if users
> > specify all the keys at the beginning of the transaction, for example
> >
> >    1. User tells Ignite which keys he/she plans to transact on
> >    2. Ignite preemptively acquires locks on all these keys
> >    3. After locks are acquired, user has assurance that values will not
> >    change outside of this transaction and are consistent with teacher.
> >    4. Locks are released upon commit
> >
> > The above algorithm will also perform better, as the initial looks will
> be
> > acquired in bulk, and not individually.
> >
> > Thoughts?
> >
> > [1]
> >
> https://apacheignite.readme.io/docs/transactions#optimistic-and-pessimistic
> >
>

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