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From Milind Parikh <milindpar...@gmail.com>
Subject Re: CounterColumns with double, min/max
Date Fri, 25 May 2012 21:56:29 GMT
On 1, countandra.org.
On 2, the issue is a little more deep (we have investigated this at
countandra). To approach it a little more comprehensively, the issue has
more to do with events rather than counts (at least in IMO).

A similar issue is about averages... countandra does sums and counts quite
easily; thanks to Cassandra's counter columns. However Averages are a
little more challenging in the eventually consistent world. Average =
Sum/Count. However which Sum and which Count? You can have a Sum and Count
from different times and divide the two and you might get a division by
zero or 0/sum.

We are investigating the use of Interval Time Clocks (ITCs) as the
mechanism for co-ordinating these times. Incidentally the use of the ITC
can be used to produce globally consistent snapshots across nodes of
Cassandra.

Regards
Milind




On Fri, May 25, 2012 at 11:55 AM, Furcy Pin <furcy@qunb.com> wrote:

> Hi all,
>
> I am currently investigating the possibilities of Cassandra for my company,
> I have played around with Hector and Cassandra for a month now, and I have
> a few questions to ask (in a separate mail for each topic).
>
> So here are my first questions:
>
> 1)
> I found the CounterColumns to be a very powerful feature. I heard that it
> was more or less the implementation of Rainbird described
> by Twitter a year ago, and was supposed to go open source one day (Cf
> http://techcrunch.com/2011/02/04/twitter-rainbird/ ) Is it true?
>
> 2)
> More seriously: do you think Cassandra-2833 will be done one day? What
> about Cassandra-1132?
> I think having CounterColumns being able to manage double and min/max
> operation would be quite useful features (at least for my company).
>
> Thanks for your time,
>
> Furcy
>
> PS: if anyone happens to live in Paris (I know :-( ), I would be glad to
> talk about Cassandra around a beer.
>

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