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From laccolithgr...@gmx.de
Subject Finding pairs of documents
Date Thu, 28 May 2009 17:36:30 GMT
Hi!

I'm quite new to CouchDB and map/reduce and played a little around
with it. Currently, I am trying to find pairs of two documents which
fulfill a special condition. E.g., consider the following documents in
the store (_id and _rev are left out): [{price: 1},{price: 5},{price:
9},{price: 1000}]

Now I would like to find all pair of documents, where (doc1.price + 4
== doc2.price). How can I express this in couchdb? I expect the
following result: [[{price: 1},{price: 5}], [{price: 5},{price:9}]]

My first try was:
map: function(doc){
  emit(null, doc);
}
reduce: function(key, values){
  for(var i in values){
    for(var j in values){
      if(values[i].price + 4 == values[j]) return [values[i], values[j]];
    }
  }
}

But then I recognized the rereduce property in CouchDB and that the
values of the reduce funtion can be only intermediate results. So how
can I express what I want to do in map reduce?

Thx!

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