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From aaron morton <aa...@thelastpickle.com>
Subject Re: wild card on query
Date Thu, 16 Aug 2012 22:29:17 GMT
> I want to retrieve all the photos from all the users of certain project. My sql like query
will be "select projectid * photos from Users". How can i run this kind of row key predicate
while executing query on cassandra?
You cannot / should not do that using the data model you have. (i.e. you could do it with
a secondary index, but in this case you probably should not).

Try to de-normalise your data. 

Say a CF called ProjectPhotos

* row key is the project_id
* column name is <timestamp:user_id>
* column value is image_url or JSON data about the image. 

You would then slice some columns from one row in the  ProjectPhotos CF. 

You then need to know what images a user has uploaded, with say the UserPhotos CF. 

* row key is user_id
* column name is timestamp
* column value is image_url or JSON data about the image. 

I did a twitter sample app at http://wdcnz.com a couple of weeks ago that shows denormalising
data  https://github.com/amorton/wdcnz-2012-site and http://www.slideshare.net/aaronmorton/hellow-world-cassandra

Hope that helps. 

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 17/08/2012, at 12:39 AM, Swathi Vikas <swat.vikas@yahoo.com> wrote:

> Hi,
> 
> I am trying to run query on cassandra cluster with predicate on row key.
> 
> I have column family called "Users" and rows with row key like "projectid_userid_photos".
Each user within a project can have rows like projectid_userid_blog, projectid_userid_status
and so on. 
> 
> I want to retrieve all the photos from all the users of certain project. My sql like
query will be "select projectid * photos from Users". How can i run this kind of row key predicate
while executing query on cassandra?
> 
> Any sugesstion will help. 
> 
> Thank you,
> swat.vikas
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