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From "Hendrijk Templehov" <nuzu...@googlemail.com>
Subject Re: CouchDB as MapReduce framework?
Date Sun, 14 Sep 2008 09:44:43 GMT
Hi Chris,

thank you for your reply.
However, I am not a Ruby programmer, but I tried to understand your
word-count example.

2008/9/14 Chris Anderson <jchris@grabb.it>:
> I did an example word count on my blog a few months ago. The post is here:
> http://jchris.mfdz.com/code/2008/5/couchdb_mapreduce_example

There are two files in your examples/-directory, word_count_query and
word_count.

As far as I understand your code, one file downloads to text files
from the gutenberg project and puts them into the database.
The other file actually runs the word_count job by retrieving all (or
one) book and then counts each word.

For getting the book-documents from CouchDB you created a common
CouchDB view ("word_count/count").

So, to come to the point: The second map/reduce job (actually counting
the words) is fully done by application logic. After the
word_count/count-view is executed to CouchDB, CouchDB itself is not
anymore related to what you're doing there. If you imagine a task
where more than one (ore more than ten) map/reduce-jobs are involved,
only the first one is executed via CouchDB itself. This way you lose
CouchDB's distributed features, because you simply rely on your own
application.

Or did I miss the point?


Kind regards
Hendrijk

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