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From gabriele renzi <rff....@gmail.com>
Subject Re: Memcached protocol?
Date Tue, 06 Apr 2010 08:23:29 GMT
On Tue, Apr 6, 2010 at 2:10 AM, Paul Prescod <paul@ayogo.com> wrote:
> On Mon, Apr 5, 2010 at 4:48 PM, Tatu Saloranta <tsaloranta@gmail.com> wrote:
>> ...
>>
>> I would think that there is also possibility of losing some
>> increments, or perhaps getting duplicate increments?
>
> I believe that with vector clocks in Cassandra 0.7 you won't lose
> anything. The conflict resolver will do the summation for you
> properly.
>
> If I'm wrong, I'd love to hear more, though.

I keep reading this in the list, but why would vector clocks allow
consistent counters in a conflicting update?
Say nodes A,B,C where A,B get concurrent updates, if we do
read-and-set this does not seem useful as we'd end up with a vector
<A:x+1,B:x+1> but why would x+1 be the correct value compared to x+2 ?

Or are we imagining spreading pairs <key,INCR>, <key,DECR> in which we
assume the writer client did not look at the existing value?


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