meh.js

var MongoClient = require("mongodb").MongoClient;

MongoClient.connect(process.env.MONGO_URI, function(err, db) {
    var users = db.collection("users");
    var places = db.collection("places");
    var one_done = 0;

    function checkDone() {
        if(one_done == 3) {
            db.close();
        } else {
            one_done += 1;
        }
    }

    function reduce(key, values) {
        var result = 0;
        values.forEach(function(value) {
            result += value;
        });
        return result;
    }

    var options = {
        out: {inline: 1},
        scope: { places: places, console: console }
    }


    /*
     * Tags distributions
     */
    users.mapReduce(function() {
        for(var i in this.bookmarks) {
            var bookmark = this.bookmarks[i];
            // Notes
            if(bookmark.tags == undefined) {
                emit(0, 1);
                break;
            } 

            // Check to see if the tags are different than the place's
            // SEGFAULT IS HERE (I think)
            places.find({ _id: bookmark.place_id });

            emit(bookmark.tags.length, 1);
            emit("1+", 1);
        }
    }, reduce, options, function(err, results) {
        console.log("\n--- tags distribution --");
        console.log(err);
        console.log(results);
        checkDone();
    });
});