How to efficiently aggregate several collections into one collection

I have four collections

1.links(movieId,imdbId,tmdbId) 
2.movies(movieId,title,genres),
3.tags(userId,movieId,tag,timestamp), 
4.ratings(userId,movieId,rating,timestamp).

Now what i need to do is aggregate them into one collection as follows

movieId,imdbId,tmdbId,
title,genres,
u_data{[
{userId,tag,tag_timestamp,
rating,rating_timestamp}
]}

How can i achieve this.

I refered link1. But couldn't comeup with an answer. (i use dataset from grouplens.org)