Question

今天我测试了Mongo数据库，但是我遇到了性能问题。在我插入1.800.00之后，我尝试将所有值的总和但它也是57s。然后我在MSSQL中尝试了同样的事情并且拿了0 !!

你能提出我做错的提示吗？这是芒果限制吗？

    static void Main(string[] args)
    {
        //Create a default mongo object.  This handles our connections to the database.
        //By default, this will connect to localhost, port 27017 which we already have running from earlier.
        var connStr = new MongoConnectionStringBuilder();
        connStr.ConnectTimeout = new TimeSpan(1, 0, 0);
        connStr.SocketTimeout = new TimeSpan(1, 0, 0);
        connStr.Server = new MongoServerAddress("localhost");
        var mongo = MongoServer.Create(connStr);

        //Get the blog database.  If it doesn't exist, that's ok because MongoDB will create it 
        //for us when we first use it. Awesome!!!
        var db = mongo.GetDatabase("blog");

        var sw = new Stopwatch();
        sw.Start();
        //Get the Post collection.  By default, we'll use the name of the class as the collection name. Again,
        //if it doesn't exist, MongoDB will create it when we first use it.
        var collection = db.GetCollection<Post>("Post");
        Console.WriteLine(collection.Count());
        sw.Stop();
        Console.WriteLine("Time: " + sw.Elapsed.TotalSeconds);

        sw.Reset();
        sw.Start();
        var starting = collection.Count();
        var batch = new List<Post>();
        for (int i = starting; i < starting + 200000; i++)
        {
            var post = new Post
            {
                Body = i.ToString(),
                Title = "title " + i.ToString(),
                CharCount = i.ToString().Length,
                CreatedBy = "user",
                ModifiedBy = "user",
                ModifiedOn = DateTime.Now,
                CreatedOn = DateTime.Now
            };
            //collection.Insert<Post>(post);
            batch.Add(post);
        }
        collection.InsertBatch(batch);
        Console.WriteLine(collection.Count());
        sw.Stop();
        Console.WriteLine("Time to insert 100.000 records: " + sw.Elapsed.TotalSeconds);

        //var q = collection.Find(Query.LT("Body", "30000")).ToList();
        //Console.WriteLine(q.Count());

        sw.Reset();
        sw.Start();
        var q2 = collection.AsQueryable<Post>();
        var sum = q2.Sum(p => p.CharCount);
        Console.WriteLine(sum);
        sw.Stop();
        Console.WriteLine("Time to sum '" + q2.Count() + "' Post records: " + sw.Elapsed.TotalSeconds); //PROBLEM: take 57 to SUM 1.000.000 records

} }

Answer 1

以下行中的性能问题：

var q2 = collection.AsQueryable<Post>();

在上面的行中，您将所有帖子从posts集合加载到内存中，因为驱动程序不支持linq。在MSSQL中，因为linq而不到秒，计算将通过数据库。在这里，我猜几乎所有57秒都需要将数据加载到内存中。

在mongodb中为了获得最佳性能，您需要创建额外的字段（de normalize data）并尽可能计算任何总和，计数器等。如果不可能，您需要使用map/reduce或可用的aggregate函数，例如group（非常适合您的和计算示例）。

关于Mongo数据库的性能问题

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