Question

I have a fairly straight forward database structure I would like to create with MongoDB. My structure looks like this:

    {url: value,
     users: {user_id: value}}

An example document might looks like this:

{'url': 'http://stackoverflow.com/', users: {'billy': 12, 'tommy': 2}}

I’m using PyMongo to update my database and add documents as show above. I can successfully add data to my database, but I cannot seem to duplicate the above data structure.

    for d in data:
        foo.update(
            {'id': d.get('url')}, 
            {'$addToSet' :{'users': {d.get('user'): 'NaN'}}},
            upsert=True)

The above code inserts but the ‘user’ structure is not what I intended. I would like:

users: {'billy': 'NaN', 'tommy': 'NaN'}

and I get:

users : [ { 'billy' : "NaN" }, { 'tommy' : "NaN" } ]

Can anyone help? Thanks for your time.

Answer 1

Per my comment above I would suggest not embedding a document but instead using an array. The following would work well:

{'url': 'http://stackoverflow.com/', 
 'users': [{'user': 'billy', 'value': 12},
           {'user': 'tommy', 'value': 2}}

This way you can leverage $push, $pull etc. as well as $addToSet. For the latter you could add a new user like this:

foo.update({'url': d.get('url')}, {'$addToSet': {'users': {'user': 'john', 'value': 0}}})

Now lets say you just wanted to increment a value for a given user, you could easily do that too:

foo.update({'url': d.get('url'), 'users.user': 'tommy'}, {'$inc': {'users.$.value': 1}})

To see more things that you could do with the schema I proposed I would read this