Test performance of ActiveRecord Includes. This is a test script designed to test for a performance regression when using the .includes() method on a scope.

gistfile1.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
ensure
  require 'benchmark'
  Benchmark.benchmark("#{Rails.version} - #{ActiveRecord::Base.configurations[Rails.env]['adapter']}\n", 40) do |x|
    x.report('limit 100 has_many') { 1.times { Item.preload(:events).limit(100).order(:id).to_a } }
    x.report('limit 100 has_many_through') { 1.times { Item.preload(:event_people).limit(100).order(:id).to_a } }
    x.report('limit 100 double has_many_through') { 1.times { Item.preload(:people).limit(100).order(:id).to_a } }
    x.report('limit 1000 has_many') { 1.times { Item.preload(:events).limit(1000).order(:id).to_a } }
    x.report('limit 1000 has_many_through') { 1.times { Item.preload(:event_people).limit(1000).order(:id).to_a } }
    x.report('limit 1000 double has_many_through') { 1.times { Item.preload(:people).limit(1000).order(:id).to_a } }
  end
end