Question

I have two models Horse and Race.

class Horse < ActiveRecord::Base
has_many :races
end

class Race < ActiveRecord::Base
belongs_to :horse
end

Now I want to use the new rails 3 query interface to see the Horse name and all its races.

Horse.joins(:races)  # I get an active record relation that only displays horse data

Horse.joins(:races).count #Yields 31 the exact number of races.

Horse.joins(:races).all #Yields an Array of 31 Horse, but no race data

Horse.joins(:races).all.select("horses.*, starters.*") #Yields active record relation with only Horse data.

Question 1: What’s the correct query to yield complete horse and race records.

Question 2: What’s the correct query to yield the horse name and all of the race record.

I know this is very basic, but I’m stumped. I sense I’d doing something wrong with the relation.

Answer 1

From what I can see I don’t thing you’re doing anything wrong with your relations.

If you want to see all horses with each of their races:

Horse.includes(:races).each do |horse|
  puts horse.name
  horse.races.each do |race|
    puts race.name
  end
end

Assuming I understand your question, your use of joins(:races) is irrelevant here. First, it will not automatically pull any data from the races table. It will simply add an inner join between horses and races. If horse N has 10 races, that query will then return 10 instances of horses N, which is probably not useful in this instance.

The includes(:races) above isn’t strictly necessary – it just loads all the races at once with one query, as opposed to n queries (n being the number of horses). Just saves time and resources.