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From Michael Zedeler <mich...@zedeler.dk>
Subject Re: how to count the number of unique values
Date Tue, 12 Oct 2010 13:18:34 GMT
  On 2010-10-12 15:09, Anand Chitipothu wrote:
> Is it possible to count the number of unique values by writing a couchdb view?
>
> Consider the following 2 docs.
>
> {
>      "_id": "posts/1",
>      "title": "post 1",
>      "tags": ["foo", "bar"]
> }
>
> {
>      "_id": "posts/2",
>      "title": "post 2",
>      "tags": ["foo", "foobar"]
> }
>
> Is it possible to find that there are 3 tags?
Yes. Just write a map function that emits all tags it finds (not checked 
and probably wrong):

function(doc) {
     for(tag in doc.tags) {
         emit(tag, null);
     }
}

In the reduce-function, just use _count 
(http://wiki.apache.org/couchdb/Built-In_Reduce_Functions).

Regards,

Michael.


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