benchmark.rb

RAILS_VERSION = '4.2.0' # switch '4.1.8' '4.2'
# Remember to rm Gemfile when switch version.
unless File.exist?('Gemfile')

  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', '#{RAILS_VERSION}'
    gem 'sqlite3'
    gem 'pg'
    gem 'byebug'
  GEMFILE

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

require 'active_record'
require 'minitest/autorun'
require 'logger'
require 'byebug'

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
# ActiveRecord::Base.logger = Logger.new(STDOUT)


ActiveRecord::Schema.define do
  create_table :issues do |t|
    t.string :title
    t.integer :tracker_id, index: true
    t.integer :category_id, index: true
    t.timestamps null: false
  end
  create_table :nested_relations do |t|
    t.string :name
    t.timestamps null: false
  end
  create_table :categories do |t|
    t.string :name
    t.timestamps null: false
  end
  create_table :trackers do |t|
    t.string :name
    t.integer :nested_relation_id, index: true
    t.timestamps null: false
  end
end

class Category < ActiveRecord::Base;
end
class NestedRelation < ActiveRecord::Base;
end
class Tracker < ActiveRecord::Base
  belongs_to :nested_relation
end

class Issue < ActiveRecord::Base
  belongs_to :tracker
  belongs_to :category
end

# Insert categories
categories_iterations = 50
categories_iterations.times do |_|
  category = Category.new
  category.name = 'hello'
  category.save
end
# Insert nested relation
nested_relations_iterations = 3
nested_relations_iterations.times do |_|
  nested_relation = NestedRelation.new
  nested_relation.name = 'hello'
  nested_relation.save
end

# Insert trackers
nested_relations = NestedRelation.all
nested_relations_count = nested_relations.size - 1

trackers_iterations = 3
trackers_iterations.times do |_|
  tracker = Tracker.new
  tracker.name = 'Tracker name'
  tracker.nested_relation = nested_relations[rand(0..nested_relations_count)]
  tracker.save
end

# Insert issues
issues_iterations = 10_000
trackers = Tracker.all
categories = Category.all
trackers_count = trackers.size - 1
categories_count = categories.size - 1
issues_iterations.times do |_|
  issue = Issue.new
  issue.title = 'Issue title'
  issue.tracker = trackers[rand(0..trackers_count)]
  issue.category = categories[rand(0..categories_count)]
  issue.save
end


ITERATIONS = 5

# Database contains :
# 10_000 issues
# 30 categories
# 3 trackers
# 3 nested_relations

Benchmark.bm(40) do |bm|
  ITERATIONS.times do |time|

    puts "\nIteration n: #{time + 1}"
    issues = Issue.all.includes(:category, tracker: :nested_relation) # To bypass cache
    bm.report("Rails #{RAILS_VERSION} : 1 relation") do
      issues.each do |issue|
        caption = issue.tracker.name
      end
    end

    issues = Issue.all.includes(:category, tracker: :nested_relation) # To bypass cache
    bm.report("Rails #{RAILS_VERSION} : 2 relations") do
      issues.each do |issue|
        caption = issue.tracker.name
        caption1 = issue.category.name
      end
    end

    issues = Issue.all.includes(:category, tracker: :nested_relation) # To bypass cache
    bm.report("Rails #{RAILS_VERSION} : 1 nested relation") do
      issues.each do |issue|
        caption1 = issue.tracker.nested_relation.name
      end
    end
  end
end