具有查找功能的mongodb聚合

Question

I have a model similar to this one:

{
  email: String,
  name: String,
  role: String,
  location: {
    country: String,
    city: String
  },
  contacts: {
    email: String,
    phone: String
  }
}

I need to show in my view the entire users information but I wish to include also how many users from a country there are.

Using aggregate I don't know how to get the full user over the groups I create.

So at the moment what I'm doing is this:

User.find({}, function(err, users) {
  User.aggregate([
    { $group: { _id: { country: '$location.country' }, count: { $sum: 1 }}}
  ], function(err, results) {
    res.render('home', {
      users: users,
      countries: results
    });
  });
});

As you can see I'm using Find and then aggregate to get both the information I need... but I'm pretty sure there is a way to get it using only aggregate but I can not find how to do that...

Answer 1

If you need to accumulate the entire user information for each group, then you need to use the $push operator for accumulation and the $$ROOT system variable to access the entire user info.

User.aggregate([
{$group:{"_id":{"country":"$location.country"},
         "users":{$push:"$$ROOT"},
         "count":{$sum:1}}}
],callback)

In case you would want to accumulate only specific fields of the user information document, you could just push the required fields like:

User.aggregate([
{$group:{"_id":{"country":"$location.country"},
         "users":{$push:{"email":"$email","name":"$name"}},
         "count":{$sum:1}}}
],callback)