NodeJs+MongoDB+Migrations

migration_script.js

/*
This script uses https://github.com/tj/node-migrate module for NodeJs

Installing:
1. npm install -g grunt-cli
2. npm install grunt --save-dev
3. npm install migrate -g

Running from console:
1. migrate create migration_script
2. migrate up migration_script.js

*/
'use strict'

var MongoClient = require('mongodb').MongoClient,
    url = 'mongodb://localhost:27017/restaurant';

exports.up = function (next) {
    MongoClient.connect(url, function (err, db) {
        var collection = db.collection('product_categories'),
            Q = require('q');
        // grouping query
        collection.aggregate([
            {
                $sort: {
                    createdAt: 1
                }
            },
            {
                $group: {
                    _id: "$restaurant",
                    ids: {$push: "$_id"}
                }
            }
        ], function (err, restaurants) {
            // response
            if(err) {
                console.error(err);
            } else {
                var ObjectID = require('mongodb').ObjectID,
                    promises = [];

                for(var i in restaurants) {
                    for(var k in restaurants[i].ids) {
                        promises.push((function() {
                            var deferred = Q.defer();
                            // add sortorder
                            collection.updateOne({_id: new ObjectID(restaurants[i].ids[k]) }, {$set:{sortorder: parseInt(k)}}).then(function(result){
                                deferred.resolve(true);
                            });

                            return deferred.promise;
                        })());
                    }
                }

                Q
                    .allSettled(promises)
                    .then(function(data) {
                        // creating index
                        collection.createIndex({restaurant:1, sortorder:1}
                            , {unique:true}, function(err, indexName) {
                                if(err) console.error(err);
                                else {
                                    next();
                                }
                                db.close();
                            });
                    }).catch(function(error) {
                        console.error(error.message);
                    });
            }
        });
    });
};

exports.down = function (next) {
    MongoClient.connect(url, function (err, db) {
        var collection = db.collection('product_categories');

        // drop index
        collection.dropIndex("restaurant_1_sortorder_1", function(err, result) {
            // drop all sortorder
            var o = {w:1};
            o.multi = true;
            collection.updateMany({}, {$unset:{sortorder:""}}, o, function(err, r) {
                db.close();
                next();
            });
        });
    });
};