Todos performance: Include associations in Finder

app/controllers/dashboard/todos_controller.rb

@@ -51,7 +51,7 @@ class Dashboard::TodosController < Dashboard::ApplicationController
   private
   def find_todos
-    @todos ||= TodosFinder.new(current_user, params).execute
+    @todos ||= TodosFinder.new(current_user, params.merge(include_associations: true)).execute
   end
   def todos_counts

app/finders/todos_finder.rb

@@ -24,6 +24,7 @@ class TodosFinder
   def execute
     items = current_user.todos
+    items = include_associations(items)
     items = by_action_id(items)
     items = by_action(items)
     items = by_author(items)
@@ -38,6 +39,17 @@ class TodosFinder
   private
+  def include_associations(items)
+    return items unless params[:include_associations]
+
+    items.includes(
+      [
+        target: { project: [:route, namespace: :route] },
+        author: { namespace: :route },
+      ]
+    )
+  end
+
   def action_id?
     action_id.present? && Todo::ACTION_NAMES.has_key?(action_id.to_i)
   end

app/helpers/todos_helper.rb

@@ -39,9 +39,13 @@ module TodosHelper
       namespace_project_commit_path(todo.project.namespace.becomes(Namespace), todo.project,
                                     todo.target, anchor: anchor)
     else
-      path = [todo.project.namespace.becomes(Namespace), todo.project, todo.target]
-
-      path.unshift(:pipelines) if todo.build_failed?
+      if todo.build_failed?
+        # associated namespace and route would be loaded from the db again if todo.project was used
+        project = todo.target.project
+        path = [:pipelines, project.namespace.becomes(Namespace), project, todo.target]
+      else
+        path = [todo.target]
+      end
       polymorphic_path(path, anchor: anchor)
     end

app/models/merge_request.rb

@@ -7,6 +7,7 @@ class MergeRequest < ActiveRecord::Base
   belongs_to :target_project, class_name: "Project"
   belongs_to :source_project, class_name: "Project"
+  belongs_to :project, foreign_key: :target_project_id
   belongs_to :merge_user, class_name: "User"
   has_many :merge_request_diffs, dependent: :destroy
@@ -540,10 +541,6 @@ class MergeRequest < ActiveRecord::Base
     target_project != source_project
   end
-  def project
-    target_project
-  end
-
   # If the merge request closes any issues, save this information in the
   # `MergeRequestsClosingIssues` model. This is a performance optimization.
   # Calculating this information for a number of merge requests requires

spec/factories/merge_requests.rb

@@ -4,6 +4,7 @@ FactoryGirl.define do
     author
     association :source_project, :repository, factory: :project
     target_project { source_project }
+    project { target_project }
     # $ git log --pretty=oneline feature..master
     # 5937ac0a7beb003549fc5fd26fc247adbce4a52e Add submodule from gitlab.com

spec/helpers/todos_helper_spec.rb

 require "spec_helper"
 describe TodosHelper do
+  include GitlabRoutingHelper
+
+  describe '#todo_target_path' do
+    let(:project)       { create(:project) }
+    let(:merge_request) { create(:merge_request, target_project: project, source_project: project) }
+    let(:issue)         { create(:issue, project: project) }
+    let(:note)          { create(:note_on_issue, noteable: issue, project: project) }
+
+    let(:mr_todo)           { build(:todo, project: project, target: merge_request) }
+    let(:issue_todo)        { build(:todo, project: project, target: issue) }
+    let(:note_todo)         { build(:todo, project: project, target: issue, note: note) }
+    let(:build_failed_todo) { build(:todo, :build_failed, project: project, target: merge_request) }
+
+    it 'returns correct path to the todo MR' do
+      expect(todo_target_path(mr_todo)).
+        to eq("/#{project.full_path}/merge_requests/#{merge_request.iid}")
+    end
+
+    it 'returns correct path to the todo issue' do
+      expect(todo_target_path(issue_todo)).
+        to eq("/#{project.full_path}/issues/#{issue.iid}")
+    end
+
+    it 'returns correct path to the todo note' do
+      expect(todo_target_path(note_todo)).
+        to eq("/#{project.full_path}/issues/#{issue.iid}#note_#{note.id}")
+    end
+
+    it 'returns correct path to build_todo MR when pipeline failed' do
+      expect(todo_target_path(build_failed_todo)).
+        to eq("/#{project.full_path}/merge_requests/#{merge_request.iid}/pipelines")
+    end
+  end
+
   describe '#todo_projects_options' do
     let(:projects) { create_list(:empty_project, 3) }
     let(:user)     { create(:user) }