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From Jonathan Ellis <>
Subject Re: forum application data model conversion
Date Mon, 28 Jun 2010 15:40:47 GMT
The principle in Cassandra modeling is that for each query, you should
denormalize your data at write time such that you can get the data for
that query from a single row.

The best explanation so far is at

On Tue, Jun 22, 2010 at 1:13 PM, S Ahmed <> wrote:
> Converting a Forum application to cassandra's data model.
> Tables:
> Posts [postID, threadID, userID, subject, body, created, lastmodified]
> So this table contains the actual question subject and body.
> When a user logs in, they want to see a list of their questions, and also
> order by the last-modified date (to see if people responed to their
> question).
> How would you do this best in Cassandra, seeing as the question/answer text
> is stored in another table.
> I know you could make a CF like:
> userID { postID1, postID2, ...}
> And somehow order by last-modified, but then on the actual web page you
> would have to first query for postID's owned by the user, and orderd by
> last-modified.
> THEN you would have to fetch the post data from the posts collection.
> Is this the only way?  I mean other than repeating the post subject+body in
> the user-to-postID index CF.

Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support

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