struggling with ember.js concepts - lots of data - ruby-on-rails

Question

I am looking at using Ember.js for a new, Rails-backed, app (using Active Model Serializers). I am struggling to get my head around the framework, so maybe this is a bit of a newbie question.
My data structure is like this (simplified):
Event Days --
Events --
* Participants
* Location
Inside of an 'Event Day' there can be thousands of events (and inside an event dozens of participants and all of their data).
It seems 'wrong' that when I want to get a listing of event days I load some JSON that has the not only the EventDays but also all the Events (and then all the data from everything inside there)... basically, it loads the whole tree!
I thought I could solve this problem by using custom Serializers for the actions, but, at some point I need to get the data and Ember seems to never call the server again.
So, if I load EventDays and simply have no event data inside it Ember never calls the server to update the EventDay object when I click through to a 'show' method.
I don't know if I am being clear here. I am hoping someone who is a little ahead of me in this can understand what I am driving at!
Really I think it boils down to 2 questions:
1)How to properly filter out information on requests so that only the local objects are filled in (i.e. on a call to an index method I need a list of event days without children, but on a call to a show method I need a single event day filled with the next level down)
2) How to get Ember to 'reload' an object at the appropriate time to fill out the appropriate content
Maybe I am looking at this wrong - missing the point of something like Ember - and if so I welcome pointers to appropriate tutorials but I can't find anything (even on the Ember site) that explains how to do anything other than load the whole tree at once. With Gigs of data, this seems slow, a definite browser-killer and just plain wrong.
I appreciate my StackOverflow brethren helping me learn!
edit
As I was immediately down voted for some reason I will add code:
Client Side:
App.EventDay = DS.Model.extend({
day: DS.attr('date'),
events: DS.hasMany("Event", {async: true})
});
Server Side:
class EventDaySerializer < ActiveModel::Serializer
attributes :id, :day
has_many :events, embed: :ids, key: :events
end
edit 2
after kertap's suggestion I added the async attribute and updated the serialiser code above.
The json is here:
{"event_day":
{"id":2,
"day":"2013-12-05",
"events":[1,2,3,4,5,6,7,8]
}
}
It is worth noting that if I do not use the key: :events parameter in the serialiser things come back as "event_ids": [1,2,3,4] which, you would think is right, but causes Ember to not see the events.
Also worth noting is that if I do this:
HorseFeeder.ApplicationSerializer = DS.ActiveModelSerializer.extend({});
Then nothing works at all! I get Error while loading route: Error: Assertion Failed: The response from a findAll must be an Array, not undefined
I really don't think it should be this difficult to get the basic wiring of Ember and Rails to work...

Answer 1

You can tell ember data that a relationship is asynchronous.
App.EventDay = DS.Model.extend({
day: DS.attr('date'),
events: DS.hasMany("Event", {async: true})
});
If you do this and get all EventDays you will get the list of EventDays from the server side. The server side should respond with the ids of the events that are contained in an event day or you can provide a url that is a link to all events. Ember won't load the events until you need them.
Then when you call the show method for an event day and in your template you get all events for that day ember data will go off and fetch the data for events.