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From Matteo Caprari <matteo.capr...@gmail.com>
Subject returning document list and a count of related documents
Date Tue, 15 Dec 2009 14:40:29 GMT
Hello.

Following a popular example, say I have tow classes of documents in my
database, posts and comments:

{ id:'post-1', type:'post', subject:'first post', body:'...'}
{ id:'post-1-comment-1', type:'comment', post:'post-1' , body:'first comment'}
{ id:'post-1-comment-2', type:'comment', post:'post-2' , body:'second comment'}

{ id:'post-2', type:'post', subject:'second post', body:'...'}
{ id:'post-2-comment-1', type:'comment', post:'post-1' , body:'first comment'}

I'd like to have view with all posts and a count of comments.

{ id:'post-1', type:'post', subject:'first post', body:'...', comments:2}
{ id:'post-2', type:'post', subject:'secong post', body:'...', comments:1}


I was able to obtain what I wanted with a list function, but I was
hoping to do it using only a view.

I've tried with the map/reduce below, but I get the reduce_overflow error
// map.js
function(doc) {
  if (doc.type == "post") {
    map([doc._id, 0], doc);
  } else if (doc.type == "comment") {
    map([doc.post, 1], doc);
  }
}

// reduce.js
function(keys, values, rereduce) {
	log('>>>>>>');
	log('>>>>>>');
	var result = {};

	if (!rereduce) {
		values.forEach(function(doc) {			
			log({doc:doc});
			// this is a question
			if (doc.type == "post" ) {
				if (result[doc._id])
					result[doc._id].subject = doc.subject;
				else
					result[doc._id] = { subject: doc.subject };
			}
			else if (doc.type == "comment") {
				if (!result[doc.post])
                                        result[doc.post] = { comments: 0 };					
				result[doc.post].comments++;					
			}
		});
	}
	else {
		values.forEach(function(value) {					
			for (var post_id in value) {
				if (!result[post_id]) result[post_id] = { subject: '', comments: 0 }
									
				if (value[post_id].subject) {
					result[post_id] = value[post_id].subject;
				}
				if (value[post_id].comments) {
					result[post_id].comments += value[post_id].comments
				}
			}
		});
	}
	log("<<<<<<");
	log("<<<<<<");
	
	return result;
}	

thanks

-- 
:Matteo Caprari
matteo.caprari@gmail.com

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