REST API with complex queries - django

Question

I don't fully understand how to make complex queries with REST API on the backend, and a backbone web app on the frontend. Say I have a user table that has a relation with a user_group table:
user.group_ref => user_group.id
If I do a GET on /api/v1/user/1/?format=json it will do something like SELECT * FROM users WHERE id = 1. Right, ok, now... how about if I wanted to JOIN with my user_group where user.group_ref = user_group.id to instantly have access to the data on user_group. I don't want to do an extra query to go and fetch that data.
Maybe I got the whole idea wrong ... Is there a simpler way?

Answer 1

REST is a set of conventions. It doesn't provide for automatic query mapping, so you need to define a service endpoint, and then implement it to return whatever you want it to.
In your case a typical way of composing the URL would be something like:
GET /groups/(groupid)/users
Which is to say "give me all users belonging to this group". Alternatively:
GET /users?group=(groupid)
Which in style is less "RESTful", but doesn't unnecessarily promote group as a top-level resource.
Either way, Backbone doesn't provide an OOTB way for populating collections from more complex resources. For anything beyond simple CRUD you'll have to implement the service call yourself, or create a separate read-only collection with url that maps to your service. Something like:
var UserGroupCollection = Backbone.Collection.extend({
url: function() { return "groups/" + this.options.groupId + "/users"; }
});
var group = new UserGroupCollection({groupId:1});
group.fetch();

Answer 2

The REST API can be implemented separately, without any relationship to the front end, it can be designed as you need.
In your case, if you are always going to get the user_group.id with the query for a user, then you should change your SQL to JOIN statements permanently: SELECT * FROM users WHERE id = 1 JOIN user_group WHERE user.group_ref=user_group.id.
If you need both queries with and without user_group info. You can design two REST methods, such as (GET /api/v1/user/1?format=json) for without group info, and (GET /api/v1/userwithgroup/1?format=json) for ones with group info.
And on the Backbone, you could have two different Models representing the two.
If you don't have millions of users in the table, the SQL with group info should be quite fast and it would be easier to just always have group info with it.

Answer 3

There is a python library called slubmber (http://slumber.in/) which is built on top of requests for the explicit purpose of REST APIs.