I am using embedded documents in MongoDB for a Rails 3 app. I like that I can use embedded documents and the values are all returned with one query and there is less load on the database server. But what happens if I want my users to be able to update properties that really should be shared across documents. Is this sort of operation feasible with MongoDB or would I be better off using normal id based relations? If ID based relations are the way to go would it affect performance to a great degree?
If you need to know anything else about the application or data I would be happy to let you know what I am working with.
Document that has many properties that all documents share.
Person
name: string
description: string
Document that wants to use these properties:
Post
(references many people)
body: string
This all depends on what are you going to do with your Person model later. I know of at least one working example (blog using MongoDB) where its developer keeps user data inside comments they make and uses one collection for the entire blog. Well, ok, he uses second one for his “tag cloud” 🙂 He just doesn’t need to keep centralized list of all commenters, he doesn’t care. His blog contains consolidated data from all his previous sites/blogs?, almost 6000 posts total. Posts contain comments, comments contain users, users have emails, he got “subscribe to comments” option for every user who comments some post, authorization is handled by the external OpenID service aggregator (Loginza), he keeps user email got from Loginza response and their “login token” in their cookies. So the functionality is pretty good.
So, the real question is – what are you going to do with your Users later? If really feel like you need a separate collection (you’re going to let users have centralized control panels, have site-based registration, you’re going to make user-centristic features and so on), make it separate. If not – keep it simple and have fun 🙂