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From alta...@ceid.upatras.gr
Subject Re: How can I get rows in groups?
Date Mon, 22 Nov 2010 09:10:56 GMT
I am not using any client, I am trying to extend Cassandra with a new API
call so that a _node_ will do that on behalf of clients. Thank you for the
answer, but it doesn't answer my question!

Alexander

> Most of the high level clients do this for you.
>
> For example, pycassa and phpcassa both do this by returning an
> iterator from get_range() and breaking it up behind the scenes.
>
> Hector also has something similar, but I think it's in the examples
> section.
>
> What client are you using?
>
> (By the way, beta1 is old and buggy! You should switch to beta3.)
>
> - Tyler
>
> On Fri, Nov 19, 2010 at 8:33 AM, <altanis@ceid.upatras.gr> wrote:
>
>> Hello,
>>
>> I would like one of the cluster's nodes to use get_range_slices() to
>> retrieve the values of a specific column for the entire keyspace. I
>> obviously don't want to do it for the whole keyspace at once, so I'd
>> like
>> to do it in groups of n, which should be configurable.
>>
>> I get the first n values using a KeyRange with the current node's local
>> token as start_token and end_token, which equals the whole keyspace.
>>
>> After that, it makes sense to have a loop, and to use each time a new
>> KeyRange with the largest key returned by the previous iteration as the
>> start_key. However, I don't know what to use as end_key, and Cassandra
>> complains that if one of (start_key, end_key) is not null, the other
>> can't
>> be either. What can I do?
>>
>> Can I use tokens? I read that a KeyRange with tokens is end-inclusive,
>> and
>> can wrap, so I can just give the local node's token as the end_token all
>> the time, so when the traversing reaches that node again, it will know
>> the
>> whole keyspace was traversed. Or are tokens different semantically?
>>
>> I am using Cassandra 0.7.0 beta1, and the OrderPreservingPartitioner.
>>
>> Alexander Altanis
>>
>>
>>
>>
>>
>>
>


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