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From J Chris Anderson <>
Subject Re: Multiple map reduce stages
Date Tue, 18 May 2010 18:16:53 GMT

On May 18, 2010, at 2:52 AM, Kropp, Henning wrote:

> Hi,
> as far as I know working with map reduce commonly involves multiple map
> and reduce stages. A view in couchdb solely consists of one map and if
> necessary one reduce stage!? To have multiple map and reduce stages one
> would have to conjunct views in couchdb!? How can I do that? Is it
> possible to give the function(doc){..} another parameter? There is the
> shows which have the extra parameter req for the http request.
> Unfortunately my javascript knowledge of the underlaying Prototype
> concept is not very funded which could be helpful here?
> Kind regards and many thanks in advanced

CouchDB Map Reduce is a realtime incremental model, so it is quite different from the Hadoop-style
batch model. Of course you can still chain map reduce by copying the rows from a view query
to a new db, and writing another view on the new db.

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