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From Dave Cottlehuber <d...@muse.net.nz>
Subject Re: iterative map reduce
Date Wed, 14 Dec 2011 08:50:52 GMT
On 14 December 2011 05:46, Dominic Tarr <dominic.tarr@gmail.com> wrote:
> hi,
>
> I need a iterative map reduce, prefurably, in couchdb.
>
> I want to be able to do a map reduce to generate unique items, then another
> map reduce to generate stats about those unique items.
>
> from what I know about couchdb at the moment, it seems like id have to do
> the first step at the document creation step, which is just ugly.
>https://mail.google.com/mail/?shva=1#inbox
> has anyone else dealt with this problem?

Hi Dom,

Cloudant do this in BigCouch which they released as open source a
while back http://support.cloudant.com/kb/views/chained-mapreduce-views
there are a few other posts on chained MR around but I don't know of a
better Couch-style implementation. Their basic approach is to copy the
view output into a new db which you'd then re-MR as required. Rinse
and repeat until complete.

Depending on your data it might be possible to implement their
view->copy to db -> new view approach yourself in native couch. It
would be interesting to do this as a couch extension using that nifty
plugin interface that hasn't been developed yet!

A+
Dave

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