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From Benjamin Black...@b3k.us>
Subject Re: Order preserving partitioning strategy
Date Sun, 22 Aug 2010 22:11:55 GMT
https://svn.apache.org/repos/asf/cassandra/trunk/src/java/org/apache/cassandra/dht/OrderPreservingPartitioner.java

On Sun, Aug 22, 2010 at 10:46 AM, Hien. To Trong <hientt@vng.com.vn> 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
it.
>
> In cassandra paper - Cassandra - A Decentralized Structured Storage System
> "Cassandra partitions data across the cluster using consistent hashing but uses an order
pre-
> serving hash function (OPHF) to do so"
>
> I wonder:
>
> 1. Cassandra still use a hash function (the other strategy is random partitioner) for
OPP?
> 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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