profile_preloading.rb

begin
  class CreateModels < ActiveRecord::Migration
    def change
      create_table :items do |t|
      end

      create_table :events do |t|
        t.belongs_to :item
      end

      create_table :event_people do |t|
        t.belongs_to :event
        t.belongs_to :person
      end

      create_table :people do |t|
      end
    end
  end

  class Item < ActiveRecord::Base
    has_many :events
    has_many :event_people, :through => :events
    has_many :people, :through => :events
  end

  class Event < ActiveRecord::Base
    belongs_to :item
    has_many :event_people
    has_many :people, :through => :event_people
  end

  class EventPerson < ActiveRecord::Base
    belongs_to :event
    belongs_to :person
  end

  class Person < ActiveRecord::Base
  end

  CreateModels.new.change

  puts "Populating Database"
  1000.times do
    Item.create
  end

  Item.all.each_with_index do |item|
    event = Event.new
    event.people.build
    event.people.build
    item.events << event
  end
rescue => e
  # Tables already exist
  # puts e.message
end

# ::RubyProf.start
StackProf.run(mode: :cpu,  out: "./stackprof-cpu-prelading-4.2-#{Time.now.strftime('%F-%H-%M-%S')}.dump") do
Item.preload(:people).limit(1000).order(:id).to_a
end