speed up ExternalWikiService#get_project_wiki_path

* This method previously iterated over all services in a project.  Now it
will directly query the ExternalWikiService for the project and filter
by active state.
* The presence of an external wiki is also cached
* When an external wiki is added or removed, the cached value is updated

CHANGELOG

@@ -4,6 +4,7 @@ v 8.11.0 (unreleased)
 
 v 8.10.0 (unreleased)
   - Fix profile activity heatmap to show correct day name (eanplatter)
+  - Speed up ExternalWikiHelper#get_project_wiki_path
   - Expose {should,force}_remove_source_branch (Ben Boeckel)
   - Disable PostgreSQL statement timeout during migrations
   - Fix projects dropdown loading performance with a simplified api cal. !5113 (tiagonbotelho)

app/helpers/external_wiki_helper.rb

 module ExternalWikiHelper
   def get_project_wiki_path(project)
-    external_wiki_service = project.services.
-      find { |service| service.to_param == 'external_wiki' }
-    if external_wiki_service.present? && external_wiki_service.active?
+    external_wiki_service = project.external_wiki
+    if external_wiki_service
       external_wiki_service.properties['external_wiki_url']
     else
       namespace_project_wiki_path(project.namespace, project, :home)

app/models/project.rb

@@ -650,6 +650,22 @@ class Project < ActiveRecord::Base
     update_column(:has_external_issue_tracker, services.external_issue_trackers.any?)
   end
 
+  def external_wiki
+    if has_external_wiki.nil?
+      cache_has_external_wiki # Populate
+    end
+
+    if has_external_wiki
+      @external_wiki ||= services.external_wikis.first
+    else
+      nil
+    end
+  end
+
+  def cache_has_external_wiki
+    update_column(:has_external_wiki, services.external_wikis.any?)
+  end
+
   def build_missing_services
     services_templates = Service.where(template: true)
 

app/models/service.rb

@@ -17,6 +17,7 @@ class Service < ActiveRecord::Base
 
   after_commit :reset_updated_properties
   after_commit :cache_project_has_external_issue_tracker
+  after_commit :cache_project_has_external_wiki
 
   belongs_to :project, inverse_of: :services
   has_one :service_hook
@@ -25,6 +26,7 @@ class Service < ActiveRecord::Base
 
   scope :visible, -> { where.not(type: ['GitlabIssueTrackerService', 'GitlabCiService']) }
   scope :issue_trackers, -> { where(category: 'issue_tracker') }
+  scope :external_wikis, -> { where(type: 'ExternalWikiService') }
   scope :active, -> { where(active: true) }
   scope :without_defaults, -> { where(default: false) }
 
@@ -212,4 +214,10 @@ class Service < ActiveRecord::Base
       project.cache_has_external_issue_tracker
     end
   end
+
+  def cache_project_has_external_wiki
+    if project && !project.destroyed?
+      project.cache_has_external_wiki
+    end
+  end
 end

db/migrate/20160718153603_add_has_external_wiki_to_projects.rb

+class AddHasExternalWikiToProjects < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  def change
+    add_column :projects, :has_external_wiki, :boolean
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20160716115710) do
+ActiveRecord::Schema.define(version: 20160718153603) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -842,6 +842,7 @@ ActiveRecord::Schema.define(version: 20160716115710) do
     t.boolean  "only_allow_merge_if_build_succeeds", default: false,     null: false
     t.boolean  "has_external_issue_tracker"
     t.string   "repository_storage",                 default: "default", null: false
+    t.boolean  "has_external_wiki"
   end
 
   add_index "projects", ["builds_enabled", "shared_runners_enabled"], name: "index_projects_on_builds_enabled_and_shared_runners_enabled", using: :btree

spec/models/project_spec.rb

@@ -458,6 +458,47 @@ describe Project, models: true do
     end
   end
 
+  describe "#cache_has_external_wiki" do
+    let(:project) { create(:project) }
+
+    it "stores true if there is an external wiki" do
+      services = double(:service, external_wikis: [ExternalWikiService.new])
+      expect(project).to receive(:services).and_return(services)
+
+      expect do
+        project.cache_has_external_wiki
+      end.to change { project.has_external_wiki }.to(true)
+    end
+
+    it "stores false if there is no external wiki" do
+      services = double(:service, external_wikis: [])
+      expect(project).to receive(:services).and_return(services)
+
+      expect do
+        project.cache_has_external_wiki
+      end.to change { project.has_external_wiki }.to(false)
+    end
+
+    it "changes to true if an external wiki service is created later" do
+      expect do
+        project.cache_has_external_wiki
+      end.to change { project.has_external_wiki }.to(false)
+
+      expect do
+        create(:service, type: "ExternalWikiService", project: project)
+      end.to change { project.has_external_wiki }.to(true)
+    end
+
+    it "changes to false if an external wiki service is destroyed later" do
+      service = create(:service, type: "ExternalWikiService", project: project)
+      expect(project.has_external_wiki).to be_truthy
+
+      expect do
+        service.destroy
+      end.to change { project.has_external_wiki }.to(false)
+    end
+  end
+
   describe '#open_branches' do
     let(:project) { create(:project) }