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From Benjamin>
Subject Re: Order preserving partitioning strategy
Date Sun, 22 Aug 2010 22:11:55 GMT

On Sun, Aug 22, 2010 at 10:46 AM, Hien. To Trong <> wrote:
> Hi,
> I am developing a system with some features like cassandra.
> I want to add order preserving partitioning strategy, but I don't know how to implement
> In cassandra paper - Cassandra - A Decentralized Structured Storage System
> "Cassandra partitions data across the cluster using consistent hashing but uses an order
> serving hash function (OPHF) to do so"
> I wonder:
> 1. Cassandra still use a hash function (the other strategy is random partitioner) for
> If so, what is the algorithm of OPHF? is it a type of minimal perfect hash function (MPHF)?
> I already read some papers about algorithms for MPHF which preserve the order of hash
value. However,
> the size of key space equals and hash value space are equal and much more smaller than
the size of key space
> (may be userid or usertaskid) in our application. How can I deal with that or I went
on the wrong track?
> 2. My system is simple. I have some servers and I use Berkeley DB to store Key/Value
(our data model is simple). Is OPP strategy useful
> when I don't have data model like cassandra? (column family for example).
> Thanks so much.

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