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From aaron morton <aa...@thelastpickle.com>
Subject Re: random partitioner and key scan
Date Fri, 20 Jul 2012 09:17:07 GMT
Repair and token moves work on ranges of Tokens, not row keys. These operations need to scan
through all the rows in the token range. 

Ordering the rows by row key locally would mean that every row on the node would have to be
scanned to find the ones whose token was in the required token range. 

Cheers

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 20/07/2012, at 4:46 AM, prasenjit mukherjee wrote:

> When a request for token change is issued ( via nodetool ) then on
> what basis a node will move some of its rows to other node, as there
> will be no way to scan rows based on MD5 hash in a given node ( if the
> keys are not prefixed with MD5 hash )
> 
> On Thu, Jul 19, 2012 at 1:43 PM, Patrik Modesto
> <patrik.modesto@gmail.com> wrote:
>> Hi Prasenjit,
>> 
>> I don't see the need to recalculate anything. One key has a one MD5
>> hash, it doesn't change. Just use the hash to select a node, than just
>> the plain key. Can you elaborate on the redistribution please?
>> 
>> Regards,
>> P.
>> 
>> On Thu, Jul 19, 2012 at 9:09 AM, prasenjit mukherjee
>> <prasen.bea@gmail.com> wrote:
>>> The probem could be while redistributing the tokens. In that case the
>>> hashes has to be recalculated on each fo the candidate node.
>>> 
>>> -Thanks,
>>> Prasenjit
>>> 
>>> On Thu, Jul 19, 2012 at 12:19 PM, Patrik Modesto
>>> <patrik.modesto@gmail.com> wrote:
>>>> Hi,
>>>> 
>>>> I know that RandomPartitioner does MD5 of a key and the MD5 is then
>>>> used for key distribution AND key ordering. I was just wondering if
>>>> it's possible to have RandomPartitioner just for key distribution and
>>>> OrderedPartitioner just for per-node key ordering. That would solve
>>>> the often requested key scan feature.
>>>> 
>>>> Regards,
>>>> Patrik


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