How can I create unique IDs for embedded documents in MongoDB?

Question

So I need to reference particular subdocuments uniquely from items in my collection. For instance:

User = {
    \'name\': \'jim\',
    \'documents: [
        {\         


        

Answer 1

All drivers have functionality for generating ObjectIds.

In the shell you just do new ObjectId():

> db.test.insert({x:new ObjectId()});
> db.test.find();
{ "_id" : ObjectId("4f88592a06c05e4de90d0bc1"), "x" : ObjectId("4f88592a06c05e4de90d0bc0") }

In Java it's new ObjectId() as well. See the API docs for your driver to see the specific syntax.