Mongoose: deep population (populate a populated field)

Question

I have Category model:

Category:
    ...
    articles: [{type:ObjectId, ref:\'Article\'}]

Article model contains ref to

Answer 1

Populating across multiple levels

Say you have a user schema which keeps track of the user's friends.

var userSchema = new Schema({
  name: String,
  friends: [{ type: ObjectId, ref: 'User' }]
});

Populate lets you get a list of a user's friends, but what if you also wanted a user's friends of friends? Specify the populate option to tell mongoose to populate the friends array of all the user's friends:

User.findOne({ name: 'Val' }).populate({
    path: 'friends',
    // Get friends of friends - populate the 'friends' array for every friend
    populate: { path: 'friends' }
});

Reference: http://mongoosejs.com/docs/populate.html#deep-populate

Answer 2

Mongoose has now a new method Model.populate for deep associations:

https://github.com/Automattic/mongoose/issues/1377#issuecomment-15911192

Answer 3

It might be a bit too late, but I wrote a Mongoose plugin to perform deep population at any arbitrary nested levels. With this plugin registered, you can populate category's articles and accounts with just a single line:

Category.deepPopulate(categories, 'articles.account', cb)

You can also specify populate options to control things like limit, select... for each populated path. Checkout the plugin documentation for more information.

Answer 4

Easiest way to accomplish this in 3.6 is to use Model.populate.

User.findById(user.id).select('-salt -hashedPassword').populate('favorites.things').exec(function(err, user){
    if ( err ) return res.json(400, err);

    Thing.populate(user.favorites.things, {
        path: 'creator'
        , select: '-salt -hashedPassword'
    }, function(err, things){
        if ( err ) return res.json(400, err);

        user.favorites.things = things;

        res.send(user.favorites);
    });
});

Answer 5

globals.models.Category.find()
  .where('issue', req.params.id)
  .sort('order')
  .populate('articles')
  .exec(function(err, categories) {

    globals.models.Account.populate(categories, 'articles.account', function(err, deepResults){

      // deepResult is populated with all three relations
      console.log(deepResults[0].articles[0].account);

    });
});

The following example is inspired by the question asked @codephobia and populates two levels of many relationships. First fetch a user, populate its array of related orders and include each orderDetail.

user.model.findOne()
  .where('email', '***@****.com')
  .populate('orders')
  .exec(function(err, user) {

    orderDetail.model.populate(user, 'orders.orderDetails', function(err, results){

      // results -> user.orders[].orderDetails[] 
    });
});

This works fine in 3.8.8 but should work in 3.6.x.

Answer 6

This concept is deep Population. Here Calendar,Subscription,User,Apartment are mongoose ODM models in different levels

Calendar.find({}).populate({
      path: 'subscription_id',model: 'Subscription',
         populate: {path: 'user_id',model: 'User',
           populate: {path: 'apartment_id',model: 'Apartment',
              populate: {path: 'caterer_nonveg_id',
                          model: 'Caterer'}}}}).exec(function(err,data){ 
                          if(!err){
                             console.log('data all',data)
                           }
                           else{
                             console.log('err err err',err)
                            }
                   });