Refactor PastIteration mounting process

It was full of N+1 queries, and getting the things very slow

Gemfile

@@ -40,6 +40,7 @@ gem 'jquery-atwho-rails'
 gem 'jquery-ui-rails'
 gem 'kaminari'
 gem 'material_icons'
+gem 'newrelic_rpm'
 gem 'pg'
 gem 'pg_search'
 gem 'platform-api'
@@ -65,35 +66,34 @@ end
 group :production do
   gem 'kgio'
   gem 'letsencrypt-rails-heroku'
-  gem 'newrelic_rpm'
   gem 'rack-cache'
   gem 'rack-timeout'
   gem 'rails_12factor'
 end
 
 group :test do
-  gem 'rspec-rails'
-  gem 'rspec-its'
-  gem 'rspec-activemodel-mocks'
-  gem 'shoulda-matchers'
   gem 'capybara'
-  gem 'poltergeist'
   gem 'capybara-screenshot'
+  gem 'codeclimate-test-reporter', require: nil
   gem 'database_cleaner'
   gem 'factory_girl_rails'
-  gem 'codeclimate-test-reporter', require: nil
+  gem 'poltergeist'
+  gem 'rspec-activemodel-mocks'
+  gem 'rspec-its'
+  gem 'rspec-rails'
+  gem 'shoulda-matchers'
+  gem 'simplecov'
+  gem 'timecop'
   gem 'vcr'
   gem 'webmock'
-  gem 'timecop'
-  gem 'simplecov'
 end
 
 group :development do
+  gem 'better_errors'
+  gem 'binding_of_caller'
+  gem 'bullet'
   gem 'letter_opener'
   gem 'letter_opener_web', '~> 1.2.0'
-  gem "better_errors"
-  gem "binding_of_caller"
-  gem "bullet"
   gem 'rubocop', '0.49.1'
 end
 

app/models/iterations/past_iteration.rb

@@ -1,23 +1,15 @@
 module Iterations
   class PastIteration
-    attr_reader :start_date, :end_date, :points, :iteration_number
+    include Virtus.model
 
-    def initialize(start_date:, end_date:, project:, iteration_number: nil)
-      @start_date = start_date
-      @end_date = end_date
-      @project = project
-      @points = points
-      @iteration_number = iteration_number
-    end
+    attribute :start_date, DateTime
+    attribute :end_date, DateTime
+    attribute :iteration_number, Integer
+    attribute :stories, Array[Story]
+    attribute :points, Integer
 
     def points
-      @points ||= stories.sum(:estimate)
-    end
-
-    def stories
-      @stories ||= @project.stories.where(
-        'accepted_at >= ? AND accepted_at <= ?', @start_date, @end_date
-      )
+      @points ||= stories.to_a.map(&:estimate).compact.sum
     end
   end
 end

app/models/iterations/project_iterations.rb

@@ -10,27 +10,49 @@ def current_iteration_start
 
     def past_iterations
       (0...length).map do |iteration_number|
-        start_date = start_date(iteration_number)
-        end_date = end_date(start_date)
-        PastIteration.new(start_date: start_date,
-                          end_date: end_date,
-                          project: @project,
-                          iteration_number: iteration_number + 1)
+        start_at = start_date(iteration_number)
+        end_at = end_date(start_at)
+
+        PastIteration.new(
+          start_date: start_at,
+          end_date: end_at,
+          stories: stories_for(start_at, end_at),
+          iteration_number: iteration_number + 1
+        )
       end
     end
 
     private
 
+    attr_reader :project
+
+    def stories_for(start_at, end_at)
+      stories.select do |story|
+        story.accepted_at >= start_at && story.accepted_at <= end_at
+      end
+    end
+
+    def stories
+      @stories ||= begin
+        project
+          .stories
+          .with_dependencies
+          .where(state: 'accepted')
+          .where.not(accepted_at: nil)
+          .order(:accepted_at)
+      end
+    end
+
     def length
       (days_since_project_start / iteration_length_in_days).floor
     end
 
     def iteration_length_in_days
-      @project.iteration_length * 7
+      project.iteration_length * 7
     end
 
     def project_start_date
-      @project.start_date
+      project.start_date
     end
 
     def start_date(iteration_number)

app/operations/iteration_operations.rb

@@ -12,16 +12,29 @@ def initialize(start_date:, end_date:, project:)
 
     def run
       {
-        stories: stories
+        stories: past_iteration.stories
       }
     end
 
     private
 
+    attr_reader :project, :start_date, :end_date
+
+    def past_iteration
+      Iterations::PastIteration.new(
+        start_date: start_date,
+        end_date: end_date,
+        stories: stories
+      )
+    end
+
     def stories
-      Iterations::PastIteration.new(start_date: @start_date,
-                                    end_date: @end_date,
-                                    project: @project).stories
+      @stories ||= begin
+        project
+          .stories
+          .with_dependencies
+          .where('accepted_at >= ? AND accepted_at <= ?', start_date, end_date)
+      end
     end
   end
 end

app/operations/story_operations.rb

@@ -56,34 +56,40 @@ class Destroy < BaseOperations::Destroy; end
   class DestroyAll < BaseOperations::DestroyAll; end
 
   class ReadAll
+    delegate :past_iterations, :current_iteration_start, to: :iterations
+
     def self.call(*args)
       new(*args).run
     end
 
     def initialize(project:)
-      @story_scope = project.stories.with_dependencies
       @project = project
-      @iterations = Iterations::ProjectIterations.new(project: project)
     end
 
     def run
       {
         active_stories: active_stories,
-        past_iterations: @iterations.past_iterations
+        past_iterations: past_iterations
       }
     end
 
     private
 
+    attr_reader :project
+
     def active_stories
-      order(@story_scope.where("state != 'accepted' OR
-        accepted_at >= ?", @iterations.current_iteration_start))
+      @active_stories ||= begin
+        project
+          .stories
+          .with_dependencies
+          .where("state != 'accepted' OR accepted_at >= ?", current_iteration_start)
+          .order('updated_at DESC')
+          .limit(ENV['STORIES_CEILING'].presence)
+      end
     end
 
-    def order(query)
-      query.order('updated_at DESC').tap do |relation|
-        relation.limit(ENV['STORIES_CEILING']) if ENV['STORIES_CEILING']
-      end
+    def iterations
+      @iterations ||= Iterations::ProjectIterations.new(project: project)
     end
   end
 end