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From Daniel Chia <danc...@coursera.org>
Subject Re: Cassandra Data Model and Surrogate Keys
Date Tue, 25 Feb 2014 21:59:19 GMT
If you look at https://github.com/Netflix/astyanax/wiki , they have both
distributed lock, as well as a uniqueness constraint recipe.

Once you get past the thrift/astyanax style code, the underlying principle
is fairly simple which you should be able to port it to CQL3.

Thanks,
Daniel


On Tue, Feb 25, 2014 at 1:26 PM, John Stager <john.stager@gmail.com> wrote:

>
> Hello Daniel,
>
> That is correct this is for user creation and collisions should be rare.
> Is the astyanax recipe a distributed lock? I do not understand what you
> mean by a combination of reads and writes?
>
> We are using cql3 with the Datastax java driver
>
> Thanks
>   *From: *Daniel Chia
> *Sent: *Tuesday, February 25, 2014 2:02 PM
> *To: *user@cassandra.apache.org
> *Reply To: *user@cassandra.apache.org
> *Subject: *Re: Cassandra Data Model and Surrogate Keys
>
> Hi John,
>
> Since this is presumably for creation of users, which should have low
> activity per user, you can use a combination of reads / writes to acquire a
> "lock" on the username. I believe astyanax has a recipe with what you want
> that works for C1.2 (although you might have to port it to CQL3 if that's
> what you're using).
>
> Thanks,
> Daniel
>
>
> On Tue, Feb 25, 2014 at 5:41 AM, <john.stager@gmail.com> wrote:
>
>> Thanks again Michael. Those are the conclusions that I came to as well.
>> For us the window is small for possible duplicate users so I think we will
>> have to do the read before like you suggested. We will also have to be able
>> to handle the case where the duplicate users exist.
>>
>> And thanks for the example cql.
>>
>> Thanks
>>
>> Sent from my BlackBerry 10 smartphone on the Rogers network.
>>   Original Message
>> From: Michael Shuler
>> Sent: Monday, February 24, 2014 11:53 PM
>> To: user@cassandra.apache.org
>> Reply To: user@cassandra.apache.org
>> Subject: Re: Cassandra Data Model and Surrogate Keys
>>
>> On 02/24/2014 09:24 PM, john.stager@gmail.com wrote:
>> > Thanks Michael, I will take a look at LWT for the future but
>> > unfortunately we are using Cassandra 1.2 ( I should have stated that,
>> > sorry). Are there any recommendations for 1.2, or do you just have to
>> > deal with him the race condition and possible duplicate data.
>>
>> I think you would need to try to perform a best effort read before write
>> in your application. I guess it depends on the amount of traffic for the
>> table. Even then, there is a small race window in that turnaround time.
>> A nasty alternative would be a distributed lock manager, or you could
>> upgrade to 2.0, if that's possible, which would be easier than messing
>> around with locking. Someone may correct me, if there are better
>> alternatives. I simple example attached.
>>
>> Michael
>>
>
>
>
>
>
>
> --
> John W Stager
>

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