Cartesian Join ( How to do using cascading )

[Raja]

Hi,

   I  would like to know is it possible that we can do Cartesian join  in Cascading.

If  anyone can give  a simple clear example to understand Cartesian join in cascading?

Thanks in Advance,

Raja

[Andre Kelpe]

You can implement custom Joins by implementing the Joiner interface
and passing it to a CoGroup instance:

http://docs.cascading.org/cascading/3.0/javadoc/cascading-core/cascading/pipe/joiner/Joiner.html

http://docs.cascading.org/cascading/3.0/javadoc/cascading-core/cascading/pipe/CoGroup.html

- Andre

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[Raja]

Hi ,

  Thanks for your reply.  Can you provide one simple example where I can see the cartesian join  being implemented in Cascading.

Thanks,

Raja

[Ken Krugler]

Assuming you have two pipes, then

Pipe cartesian = new CoGroup(“cartesian join”, p1, Fields.NONE, p2, Fields.NONE, new OuterJoin());

should do the trick.

If one of the pipes has a relatively small number of tuples, then it’s going to be much more efficient to use a HashJoin instead of a CoGroup (just make sure p2 is the pipe with the small number of tuples)

— Ken

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Ken Krugler

+1 530-210-6378

http://www.scaleunlimited.com

custom big data solutions & training

Hadoop, Cascading, Cassandra & Solr

[Baskar]

Great.  That worked.  Thanks for your quick response.

Baskar