Group (By) in Mongoose?

Question

I\'ve constructed the query I want in the shell but am having trouble writing it in Mongoose.

db.commentstreams.group({ key: { page_id: true }, reduce: function(         


        

Answer 1

MapReduce should be the proper way to go but if you're not sharding and your query won't result in more than 10k records its ok.

You can access any node-mongodb-native functions through moongoose, so it looks like this:

var group = {
   key: {},
   cond: {item_id: item_id},
   reduce: function(doc, out) {
      out.count++;
      out.total += doc.value;
   },
   initial: {
       total: 0,
       count: 0
   },
   finalize: function(out) {
       out.avg = out.total / out.count;
   }
};

Item.collection.group(group.key, group.cond, group.initial, group.reduce, group.finalize, true, function(err, results) {
    console.log('group results %j', results);
});

node-mongodb-native source: https://github.com/mongodb/node-mongodb-native/blob/master/lib/mongodb/collection.js#L1165

MongoDB group doc: http://www.mongodb.org/display/DOCS/Aggregation#Aggregation-Group

Answer 2

According to this post:

Model.find({}, [fields], {'group': 'FIELD'}, function(err, logs) { 
        ... 
}); 

Unfortunately we seem to be lacking documentation for this one.

Answer 3

I worked with similar example, I hope this be helpful

Register.aggregate(
[
  {
   $group: {_id: {campaign: "$campaign"}, quantity: {$sum: 1}}
},
  {
    $limit: 5
  },
  {
    $sort: {date: -1}
  }
], function (err, res) {
        console.log(res)
});

Answer 4

if you're trying to use Mongoose to group maybe you're better take a look at this Mongoose group query in node.js / express route

It seems group is not supported by Mongoose while aggregate is.