How to query for a dictionary in Mongo Document?

Question

I have a Document, shown below

This is my C# structure for that document

public class MetaData
{
  [BsonId]
  public ObjectId _Id { get; set; }
  [BsonElement("User")]
  public IDictionary<Int64, FirstUser> User { get; set; }
}

public class FirstUser
{
    [BsonElement("Name")]
    public String Name { get; set; }
    [BsonElement("Id")]
    public Int64 Id { get; set; }
}

This is my BSON structure for that document

/* 1 */
{
    "_id" : ObjectId("5805c1ced520b54bd4192214"),
    "User" : [ 
        [ 
            NumberLong(1), 
            {
                "Name" : "FirstUser",
                "_id" : NumberLong(1)
            }
        ]
    ]
}

/* 2 */
{
    "_id" : ObjectId("5805c1ced520b54bd4192215"),
    "User" : [ 
        [ 
            NumberLong(1), 
            {
                "Name" : "SecondUser",
                "_id" : NumberLong(2)
            }
        ]
    ]
}


/* 3 */
{
    "_id" : ObjectId("5805c1ced520b54bd4192216"),
    "User" : [ 
        [ 
            NumberLong(1), 
            {
                "Name" : "ThirdUser",
                "_id" : NumberLong(3)
            }
        ]
    ]
}


/* 4 */
{
    "_id" : ObjectId("5805c1ced520b54bd4192217"),
    "User" : [ 
        [ 
            NumberLong(1), 
            {
                "Name" : "FourthUser",
                "_id" : NumberLong(2)
            }
        ]
    ]
}

I need all documents which are having "Name" as "FirstUser", For this how do I form MONGO QUERY?

Your BSON schema and your classes do not seem to match... your BSON seems to have "User" as array of object array instead of just the dictionary. — Felipe Sabino, Oct 18 '16 at 11:57
Can i propose you to use Aggregation Framework to resolve it? If yes, i can write you an answer. — Daniele Tassone, Oct 18 '16 at 14:45
I already tired that it was working, But the problem here is I am not able to fetch more than 16 MB. Some times i have to fetch more than 16 MB. — Gopinath Navaneethan, Oct 19 '16 at 04:52

score 1 · Answer 1 · answered Oct 18 '16 at 12:17

1

The problem here is that your dictionary keys are numbers. Usually you'd use something like "User.1.Name": "FirstUser", but this syntax actually does something else: looking for the second element in User which has Name=FirstUser (because the indexing is zero-based).

If you have only one key in User, you can use "User.0.Name": "FirstUser".

answered Oct 18 '16 at 12:17

Tomer

1,376
9
18

This works, But problem here is user can be any where we can't tell that it always come first in dictionary. – Gopinath Navaneethan Oct 19 '16 at 04:54
Can you give an example for your schema when it's the case? – Tomer Oct 19 '16 at 10:57

Kevin Smith · Answer 2 · 2016-12-14T08:11:16.580

1

You can do it from the mongo shell using the following:

db.collection.find({'User.Name': 'FirstUser'});

Or from the c# driver you can do the following:

var c = await wat.FindAsync(x => x.User[0].Name == "FirstUser");
var metaData = await c.ToListAsync();

edited Dec 14 '16 at 08:11

answered Oct 18 '16 at 15:10

Kevin Smith

10,855
1
33
59

actually i need mongo query, Because first i make query then i try to take the document. How to make make for that – Gopinath Navaneethan Oct 19 '16 at 04:47

How to query for a dictionary in Mongo Document?

2 Answers2