Object mapping solution - object

Question

I have this SQL Database structure. A users table, a objects table and a mapping table users_objects_map to assign objects to an user account.
In SQL it works fine. With this structure it is easy to fetch objects of an user or users assigned to an object. I also can assign an object to multiple users.
users
id
firstname
lastname
...
objects
id
...
users_objects_map
user_id
object_id
What is the best way to build this with MongoDB?
My first idea was to add an array to the users where all IDs of assign objects will stored.
{"firstname":"John", "lastname": "Doe", "object_ids":["id","id2",...,"id-n"]}
But what is if a user is assigned to thousands of objects? I don't think that's a good solution. And how I'm able to fetch all users assigned to an object or all objects assigned to an user?
Is there any clever MongoDB solution for my problem?

Answer 1

Using object IDs within BsonArrays as a reference towards the objects is a great way to go and also consider using BsonDocuments within the "object_ids" of the user itself, then you will be able to scale it easier and using the "_id" (ObjectID) so that MongoDB indexes those IDs, this will gain performance.
Eventually you will be having 2 collections, one is with users and the other is with objects:
user:
{
"_id" : "user_id",
"firstname" : "John",
"lastname" : "Doe",
"object_ids" : [
{ "_id" : "26548" , "futurefield" : "futurevalue" },
{ "_id" : "26564" , "futurefield" : "futurevalue" }
]
}
At this moment I really don't know what kind of objects they are going to be.. but i can give you an example:
workshop object:
{
"_id>" : "user_id",
"name" : "C# for Advanced Users",
"level" : "300",
"location" : "Amsterdam, The Netherlands",
"date" : "2013-05-08T15:00:00"
}
Now comes the fun part and that is querying.
I am developing in C# and using the driver from mongodb.org.
Example:
Give me everyone that has object id == "26564".
var query = from user in userCollection.Find(Query.EQ("objects_ids._id","26564"))
select user;
This query will return the documents, in this case the users that have matched the ID.
If you have a range of values please use: Query.All("name" , "BsonArray Values");
The second query is find and/or match the IDs of the objects ID that BsonDocuments might contain.
var secondQuery =
from workshops in objectsCollection.Find(Query.EQ("_id", "userid"))
select cust["object_ids"].AsBsonArray.ToArray();
I hope I have helped you this way.
Good luck with it!