Hi,

we have a database design with a sub-document in the _id field. Now we have the problem the the field order matters (compare documentation http://docs.mongodb.org/manual/core/index-single/#indexes-on-subdocuments) and the following example:

db.test.insert({"_id":{"uid":1, "city":"Munich"}})
db.test.insert({"_id":{"uid":2, "city":"Munich"}})
db.test.insert({"_id":{"uid":3, "city":"Munich"}})
db.test.insert({"_id":{"uid":2, "city":"Frankfurt"}})
> db.test.find({"_id":{"uid":2, "city":"Munich"}})
{ "_id" :

{ "uid" : 2, "city" : "Munich" }

}
>
> db.test.find({"_id":{"city":"Munich", "uid":2 }})
NO RESULT

What is the best solution to solve our issue? Do we have to redesign our complete data structure?

Thanks a lot
Markus