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From Pedro Gomes <>
Subject Re: An ORM like plugin for Cassandra under Datanucleus
Date Sat, 22 May 2010 10:24:27 GMT

Thank you 
Pedro Gomes

On May 22, 2010, at 2:07 AM, Jonathan Ellis wrote:

> Thanks!
> You should probably add it to
> On Fri, May 21, 2010 at 12:22 PM, Pedro Gomes
> <> wrote:
>> Hi all
>> In the following weeks I have developed a plugin to the java persistence
>> platform Datanucleus, similar to the one presented by Google for App Engine
>> and a Hbase already present in the platform .
>> Datanucleus:
>> For now it allows the persistence of simples fields and one-one, one-many,
>> and many-many relations, supporting collections and maps, arrays are next
>> through the Java Data Objects (JDO) API.
>> The platform allows a query language JDOQL, but I didn't add the support for
>> it.
>> You can access the project under :
>> Any feedback or doubts are welcome.
>> I still have, though, some doubts on the implementation. To store many-many,
>> and one to many relations in Cassandra, i.e., one collection/map of pointers
>> to other objects I see two options:
>> -The column, in the Column family class, correspondent to the relation
>> contains a collection or map that codes the relation, i.e. it stores the ids
>> to the objects,. This can be dangerous if the collection/map grows large.
>> -You have a column family that codes relations, one simple Column family per
>> relation, or a Super Column family that codes all relations . This approach
>> however,  makes each fetch from the collection takes 3 read steps, but each
>> object id is stored separately.
>> Other option that I'm thinking is a hybrid solution where the user chooses
>> the pretended option.
>> If someone can give some advice on this, I would be thankful.
>> Grateful
>> Pedro Gomes
> -- 
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of Riptano, the source for professional Cassandra support

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