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From J Chris Anderson <>
Subject Re: map/reduce
Date Tue, 02 Mar 2010 23:24:10 GMT

On Mar 2, 2010, at 3:17 PM, Don Park wrote:

> I've been getting into couchdb and learning about map/reduce. I have
> read about it before but writing my own map and reduce functions and
> playing with simple datasets have been really eye-opening. There is
> one area that I'm still trying to grasp. CouchDB is built on
> map/reduce but it doesn't seem to use map/reduce in a distributed
> fashion. If i call a couchdb server process a "node", i can issue a
> query to a node and have it map/reduce the answer. I can start five
> nodes and they can keep in sync. I can send five queries and have each
> of the five nodes work on the answer to their question. What I thought
> the "big win" as far as map/reduce is, is to issue one query and have
> it divided amongst the five nodes to get the answer with some kind of
> linear speedup for that one answer.

This can be done using the open source CouchDB-Lounge project:

Also, Cloudant has an Erlang version of this running in their hosted service:


> Thanks in advance,
> Don

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