MapReduce for counting parameter values

Posted by cnkt on Stack Overflow See other posts from Stack Overflow or by cnkt
Published on 2010-12-27T02:56:24Z Indexed on 2010/12/27 6:54 UTC
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I have document like this:

{
   "_id": ObjectId("4d17c7963ffcf60c1100002f"),
   "title": "Text",
   "params": {
     "brand": "BMW",
     "model": "i3"
    }
}

{
   "_id": ObjectId("4d17c7963ffcf60c1100002f"),
   "title": "Text",
   "params": {
     "brand": "BMW",
     "model": "i5"
    }
}

What i need is the count of every params values. like:

brand
---------
BMW (2)

model
---------
i3 (1)
i5 (1)

I think i have to write map/reduce functions. How can i do this? Thanks.

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