I need an advice about NoSQL/MongoDb and data/models structure

Question

Recently I'm exploring NoSQL Databases. I need an advice about how to store data in the most optimal and efficient way for a given problem. I'm targeting MongoDB, now. However it should be the same with CouchDB.

Let's say we have these 3 Models:

Story:
 id
 title

User:
 id
 name

Vote:
  id
  story_id
  user_id

I want to be able to ask the database these questions:

• Who has voted for this Story?
• What this User has Voted for?

I'm doing simple joins while working with a relational DB. The question is, how should I store the data for those objects in order to be most efficient.

For example, if I store the Vote objects as a subcollection of Stories it wont be easy to get the info - "What a user has voted for".

Answer 1

I would suggest storing votes as a list of story _ids in each user. That way you can find out what stories a user has voted for just by looking at the list. To get the users who have voted for a story you can do something like:

db.users.find({stories: story_id})

where story_id is the _id of the story in question. If you create an index on the stories field both of those queries will be fast.

Answer 2

• don't worry if your queries are efficient until it starts to matter
• according to below quote, you're doing it wrong

The way I have been going about the mind switch is to forget about the database alltogether. In the relational db world you always have to worry about data normalization and your table structure. Ditch it all. Just layout your web page. Lay them all out. Now look at them. Your already 2/3 there. If you forget the notion that database size matters and data shouldn't be duplicated than your 3/4 there and you didnt even have to write any code! Let your views dictate your Models. You don't have to take your objects and make them 2 dimensional anymore as in the relational world. You can store objects with shape now.

how-to-think-in-data-stores-instead-of-databases