Question

Let’s say for example i have 2 collections Comments and Users.The comments include username and the comment and Users has username and avatar. When retrieving the comments i also want to display the avatars, how should i query the two collections ? My first thought was to get all the comments and then iterate though the usernames and query the user collection to get the avatars. Can i do this differently ? Using nodejs and mongoose

Answer 1

Populate is likely what you’re looking for:

http://mongoosejs.com/docs/populate.html

Pasting some in here for posterity:
ObjectIds can now refer to another document in a collection within our database and be populate()d when querying. An example is helpful:

var mongoose = require('mongoose')
 , Schema = mongoose.Schema

var PersonSchema = new Schema({
  name    : String
  , age     : Number
  , stories : [{ type: Schema.ObjectId, ref: 'Story' }]
});

var StorySchema = new Schema({
  _creator : { type: Schema.ObjectId, ref: 'Person' }
  , title    : String
  , fans     : [{ type: Schema.ObjectId, ref: 'Person' }]
});

var Story  = mongoose.model('Story', StorySchema);
var Person = mongoose.model('Person', PersonSchema);