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:
http://www.datanucleus.org/project/download.html
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 :
http://github.com/PedroGomes/datanucleus-cassandra
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
