Query nested objects from MongoDB

Question

I created a script in SSIS to retrieve data from MongoDB. While I don't have any issues querying regular documents, I am not sure how to retrieve values from nested documents. For example, "Address" expanded contains "Country", "State", "City", "Street", and "Zip". I am interested in retrieving the "Country" (field) values only. In theory, I understand that it should be something like "Address.Country", but I do not know how to implement it in my code. What is the best way to achieve that?

This is the code that retrieves all the other documents:

    public override void CreateNewOutputRows()
    {
        string connectionString = "mongodb://localhost";
        MongoServer myMongo = MongoServer.Create(connectionString);
        myMongo.Connect();
        var db = myMongo.GetDatabase("UserDB");
        /*ICursor<BsonDocument> cursor = db.GetCollection<BsonDocument>("UserDB").FindAll();*/
        foreach (BsonDocument document in db.GetCollection<BsonDocument>("UserDB").FindAll())
        {
            this.UserDBBuffer.AddRow();
            this.UserDBBuffer.ID = document["_id"] == null ? "" : document["_id"].ToString();

            this.UserDBBuffer.PrimaryEmail = document["primary_email"] == null ? "" : document["primary_email"].ToString();
            this.UserDBBuffer.Gender = document["gender"] == null ? "" : document["gender"].ToString();

        }
}

Robert Stam · Accepted Answer · 2011-12-28 22:27:38Z

5

You can do that in C# using SetFields on the cursor returned by FindAll:

var fields = Fields.Include("Address.Country");
foreach (var document in collection.FindAll().SetFields(fields))
{
    Console.WriteLine(document.ToJson());
}

You can extract the Country value from the returned document using:

var country = document["Address"].AsBsonDocument["Country"].AsString;

answered Dec 28, 2011 at 22:27

Robert Stam

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2 Comments

Pasha Over a year ago

Now, the next challenge is how to extract data from an array. For example, one of the arrays looks like this: "devices -> Document -> device_data -> model" or "devices -> Document -> device_data -> brand". How do I extract the model or the brand of the device? Again, thanks a lot for your help!

Pasha Over a year ago

I changed "Address" to "location" (another field containing country) and my scripts returns "country not found" and I can't figure out why...

Sergio Tulentsev · Accepted Answer · 2011-12-28 20:11:05Z

0

db.users.find({_id: user_id},
              {'address.country': 1});

This will get you a document like

{"_id": ObjectId('4efb78234ee9184d8b5a4e92'), 
 "address": {"country": "Russia"}}

answered Dec 28, 2011 at 20:11

Sergio Tulentsev

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