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From Philippe <watche...@gmail.com>
Subject Re: Decorator Algorithm
Date Mon, 27 Jun 2011 10:02:59 GMT
a quick followup on this : when using Byte ordered partitioner. how does a
short key get mapped to the 128bit token ? what about keys longer than 128 ?
does Cassandra just pad and truncate ?

thanks
Le 24 juin 2011 04:53, "Maki Watanabe" <watanabe.maki@gmail.com> a écrit :
> A little addendum
>
> Key := Your data to identify a row
> Token := Index on the ring calculated from Key. The calculation is
> defined in replication strategy.
>
> You can lookup responsible nodes (endpoints) for a specific key with
> JMX getNaturalEndpoints interface.
>
> maki
>
>
> 2011/6/24 aaron morton <aaron@thelastpickle.com>:
>> Various places in the code call IPartitioner.decorateKey() which returns
a DecoratedKey<T> which contains both the original key and the Token<T>
>>
>> The RandomPartitioner md5 to hash the key ByteBuffer and create a
BigInteger. OPP converts the key into utf8 encoded String.
>>
>> Using the token to find which endpoints contain replicas is done by the
AbstractReplicationStrategy.calculateNaturalEndpoints() implementations.
>>
>> Does that help?
>>
>> -----------------
>> Aaron Morton
>> Freelance Cassandra Developer
>> @aaronmorton
>> http://www.thelastpickle.com
>>
>> On 23 Jun 2011, at 19:58, Jonathan Colby wrote:
>>
>>> Hi -
>>>
>>> I'd like to understand more how the token is hashed with the key to
determine on which node the data is stored - called decorating in cassandra
speak.
>>>
>>> Can anyone share any documentation on this or describe this more in
detail?   Yes, I could look at the code, but I was hoping to be able to read
more about how it works first.
>>>
>>> thanks.
>>
>>
>
>
>
> --
> w3m

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