I have a problem where I want to be able to get all the unique cities for a collection, and my code looks something like this:

var mongoose = require("mongoose"),
Schema = mongoose.Schema;

var PersonSchema = new Schema({
    name: String,
    born_in_city: String
});
var Person = mongoose.model('Person', PersonSchema);

In native MongoDb I could just do db.person.distinct("born_in_city"), but there doesn't seem to be anything equivalent for Mongoose. Is the only option to iterate over all of the documents myself to do this, or is there a better solution?

In an attempt to use the underlying node-mongodb-native as suggested by the answerer I attempted to do this:

mongoose.connection.db.collections(function(err, collections){
  collections[0].distinct('born_in_city', function( err, results ){
    console.log( err, results );
  });
});

However the results is empty and there's no error. I would also prefer to be able to fetch only the needed collection by name rather than have to filter what collections return if at all possible.

Just to give an update for Mongoose 3.x:

MyModel.find().distinct('_id', function(error, ids) {
    // ids is an array of all ObjectIds
});