MongoDB performance is slower with C # driver, not command line

I am researching MongoDB to check if we can / will use it as a noSQL store for our product. Everything seems to be working fine, but it is rather slow in our C # application. Queries take 120 to 140ms to return results, which is unacceptable for our application (more than 10x slower compared to MS SQL). At first I thought it might have something to do with the operator $in

and the fields Guid

that I was filtering, but it doesn't.

At the moment I have created a small benchmark to measure the performance of a specific query. The method looks like this:

public IQueryable<T> QueryTest<T>(string collection, IEnumerable<Guid> shouldBeIn, string fieldName)
{
    var dataModelCollection = MongoDatabase.GetCollection<T>(collection);
    var findResult = dataModelCollection
                            .FindAll()
                            .ToList();  //Doing this on purpose, so the query is executed immediatly. Just for this test!
                                        //This action takes about 110~140ms.
    return findResult.AsQueryable();
}

      

        
        
        
      

    

Obviously this is test code as I would not be ToList()

in real code and would return later IQueryable

.

When I run this query in MongoDB console, it returns 0ms result (as explained)

> db.StoreData.find().explain()
{
        "cursor" : "BasicCursor",
        "isMultiKey" : false,
        "n" : 21,
        "nscannedObjects" : 21,
        "nscanned" : 21,
        "nscannedObjectsAllPlans" : 21,
        "nscannedAllPlans" : 21,
        "scanAndOrder" : false,
        "indexOnly" : false,
        "nYields" : 0,
        "nChunkSkips" : 0,
        "millis" : 0,
        "server" : "mymongodbserver:27017",
        "filterSet" : false
}

      

        
        
        
      

    

There is an index in the field here _id

, and also one in the field StoreId

, because I want to filter later StoreId

.

Both C # and Console requests run on the same machine. I also ran the test several times and ran the command several times .reIndex()

.

Any ideas on how to proceed?

change

It is a very small database with very few test data / records. As requested, there are 21 entries , I think the result of the method explain()

also reports this. I also ran toArray()

. I don't understand how this helps, but this is part of the result, since copying 21 objects here is probably not very useful.

{
        "_id" : ObjectId("542e847e048b8b0f704a7834"),
        "StoreId" : BinData(3,"/FQLn0k/hkSofM9WvEsNKQ=="),
        "Shelves" : [
                {
                        "ShelveId" : BinData(3,"iCDhfhi6z0adh2haWjrzoQ=="),
                        "Name" : "Shelve 1",
                        "Type" : 0
                }
        ],
        "Doors" : [ ]
},
{
        "_id" : ObjectId("542e847e048b8b0f704a7835"),
        "StoreId" : BinData(3,"p7TkqeFrGEOAWtv0RZ4YjQ=="),
        "Shelves" : [ ],
        "Doors" : [ ]
},

      

        
        
        
      

    

edit2

I added some more data to the collection StoreData

to see if returning a large number (100,000) of documents is faster or slower. In MongoDB ( mongodb.exe

) client I am getting huge fast results.

> db.StoreData.find().explain()
{
        "cursor" : "BasicCursor",
        "isMultiKey" : false,
        "n" : 100021,
        "nscannedObjects" : 100021,
        "nscanned" : 100021,
        "nscannedObjectsAllPlans" : 100021,
        "nscannedAllPlans" : 100021,
        "scanAndOrder" : false,
        "indexOnly" : false,
        "nYields" : 781,
        "nChunkSkips" : 0,
        "millis" : 53,
        "server" : "cp-crossbario:27017",
        "filterSet" : false
}

      

        
        
        
      

    

As you can see, about 100,000 results are returned in 53 milisecconds .

Running the method FindAll().ToList()

with the MongoDB driver results in the entire document in 5075 milliseconds . Quite a difference!

A little more background information on the machines I run on: I created two Azure Standard_A2 machines (2 cores, 3.5GB memory) in the Western Europe region.

One of the machines is running a MongoDB database. I installed this on C:\MongoDB

and the data directory on C:\MongoDB\bin\data

. This is just for testing. No real production system should set there a date on this disc, of course.

The testing database is about 135 MB.

On another machine, I have test clients installed, a console application using the MongoDB C # driver and the MongoDB.exe file. Both connect to the database through the same HTTP endpoint.

Edit3

I just ran the method QueryTest

without <T>

, so now I am returning 'raw' BsonDocument

s. Strange, it's even slower. 100.000 documents now return ~ 8000ms, returning POCOs they return in ~ 5000ms.