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From "Hendrijk Templehov" <nuzu...@googlemail.com>
Subject Re: CouchDB as MapReduce framework?
Date Sun, 14 Sep 2008 20:47:50 GMT
Hi Chris,


2008/9/14 Chris Anderson <jchris@grabb.it>:
> You're correct that CouchDB does not currently support chained
> map-reduce jobs. This is because the incremental update feature (where
> only changes to the database have to be taken into account between
> queries to the view) doesn't have a facility to expire view-rows that
> are attached to original documents only through another map/reduce
> job.

OK. Thank you for your information.
There is another Erlang based project handling map/reduce data mining
called Disco (http://discoproject.org/). It does not ship a database
but perhaps it is possible to use CouchDB as data input for Disco?
Does anybody know?

> Group_level examples are available in the CouchDB unit tests (see reduce):
> http://svn.apache.org/repos/asf/incubator/couchdb/trunk/share/www/script/couch_tests.js
>
> There is also some example code from me that uses group_level:
> http://jchris.mfdz.com/code/2008/6/markov_chains_using_couchdb_s_g

Thank you for your links. Since using map/reduce for data mining and
clustering is still a bit scary to me and CouchDB tought me the real
advantadge of m/r even in a not chained way, I think I will continue
read documentation and code. Thank you very much for your help so far!


Kind regards
Hendrijk

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