Hello!

There are collections

city:

{"_id", "name"}

company:

{"_id", "name", "cityID"}

comments:

{"_id", "text", "companyID"}

You must select the last 10 comments on companies of a certain city.

Now I select _id first of all companies in the city, and then the 10 comments received on _id
Here's the code:

$ db-> execute ('function () {

var result = {};

var company = [];
result.company = [];
db.company.find (

{"city": "msk"}

,

{"title": 1, "_id": 1}

). forEach (function (a) {
result.company [a._id] = Object.deepExtend (a, result [a._id]);
company.push (a._id);
});

var comments = [];
result.comments = [];
db.comments.find ({"company": {"$ in": company}}). sort (

{"createTime": -1}

). limit (10). forEach (function (a)

{ result.comments [a._id] = Object.deepExtend (a, result [a._id]); comments.push (a._id); }); return result; }

');

Esti's a better option to do what I need?
Thanks in advance for your advice!