Hi,
Let's say you have a +1 or -1 vote for a given document. You could
record this with a document like:
{
"article" : "article-id", "vote": 1, "timestamp": now()
}
or
{
"article" : "article-id", "vote": -1, "timestamp": now()
}
(where now() is some function you run client side to get the time.
You'd then be able to get the rating via a simple map function and a _sum
reduce:
function(doc) {
if (doc.vote) emit(doc.article, doc.vote);
}
And query it for a specific article with
http://localhost:5984/voting/_design/vote/_view/vote?group=true&key=%22foo%22
Mike Miller did a nice summary of how you could do time binned data for your
historical info (using the timestamp field in the vote doc) on
http://nosqltapes.com/video/understanding-mapreduce-with-mike-miller
HTH
Cheers
Simon
On 25 Feb 2011, at 03:51, He Shiming wrote:
> Hi,
>
> I've got a design question. The scenario is: the database stores a
> series of articles, and each article can be commented and rated.
>
> For articles, naturally I'll have {"_id": "article-id", "type":
> "article" ...} . And each article is a single document in the
> database.
>
> I'm not sure what form should I use to put ratings and comments. I
> would like to keep a history of rating and comments for each article,
> but still be able to calculate average rating easily. I may also need
> "likes" and "dislikes" for each of the comment. So it'll be sorted in
> a custom order.
>
> How do I design documents to store such information? Thanks!
>
> --
> Best regards,
> He Shiming
