fix _key_value unique values

fix_values.js

/*globals require, console, process */
'use strict';

var nconf = require('nconf');
var async = require('async');

nconf.file({
	file: 'config.json'
});

nconf.defaults({
	base_dir: __dirname,
	views_dir: './build/public/templates',
});

var db = require('./src/database');

db.init(function(err) {
	if (err) {
		console.log("NodeBB could not connect to your database. Error: " + err.message);
		process.exit();
	}

	fixValues(function (err) {
		if (err) {
			console.error(err);
			process.exit();
		}
		console.log('done');
		process.exit();
	});
});

function fixValues(callback) {
	var client = db.client;
	async.waterfall([
		function (next) {
			client.collection('objects').aggregate([
				{
					$match: {
						_key: { $exists: true },
						value: { $exists: true },
						score: { $exists: true }
					},
				},
				{
					$group: {
						_id: { _key: '$_key', value: '$value' },
						count: { $sum: 1 }
					}
				},
				{
					$match: {
						count : {$gt: 1}
					}
				}
			], { allowDiskUse: true }).toArray(next);
		}, function (data, next) {
			async.eachSeries(data, function (item, next) {
				var dummyArray = new Array(item.count - 1);
				async.eachSeries(dummyArray, function (dummy, next) {
					console.log('removing', { _key: item._id._key, value: item._id.value });
					client.collection('objects').deleteOne({ _key: item._id._key, value: item._id.value }, next);
				}, next);
			}, next);
		},
	], callback);
}