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Subject: Re: how to count the number of unique values
From: Wout Mertens <wout.mertens@gmail.com>
In-Reply-To: <AANLkTi=_929-L5Oa7g07iFzntjFoiMNW4B7PzQXQ7eWv@mail.gmail.com>
Date: Fri, 15 Oct 2010 14:33:53 +0200
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To: user@couchdb.apache.org

Just wanted to add that if you have a map function that emits (tag, 1) =
for each tag and then a reduce function that's just _count, you will =
have everything you need for painting a tag cloud.

The view with group=3Dtrue will list all tags exactly once, with their =
count. CouchDB doesn't tell you how many rows are in the result so =
you'll have to count them yourself.

So you load that entire view in memory and you can draw the tags with =
their relative sizes.

Wout.

On Oct 12, 2010, at 15:09 , Anand Chitipothu wrote:

> Is it possible to count the number of unique values by writing a =
couchdb view?
>=20
> A typical example is to find the number of tags in a blog application.
>=20
> Consider the following 2 docs.
>=20
> {
>    "_id": "posts/1",
>    "title": "post 1",
>    "tags": ["foo", "bar"]
> }
>=20
> {
>    "_id": "posts/2",
>    "title": "post 2",
>    "tags": ["foo", "foobar"]
> }
>=20
> Is it possible to find that there are 3 tags?
>=20
> Anand