Merge branch 'events-performance' into 'master'

Improve performance of retrieving last update times for events

See 75195eefcca4cb3961986c90c8e837da02f30134 and
https://gitlab.com/gitlab-org/gitlab-ce/issues/12415#note_3387317
for the juicy details.

Related issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/12415

See merge request !2613

app/controllers/dashboard/projects_controller.rb

@@ -36,7 +36,7 @@ class Dashboard::ProjectsController < Dashboard::ApplicationController
   private
 
   def load_events
-    @events = Event.in_projects(@projects.pluck(:id))
+    @events = Event.in_projects(@projects)
     @events = @event_filter.apply_filter(@events).with_associations
     @events = @events.limit(20).offset(params[:offset] || 0)
   end

app/controllers/dashboard_controller.rb

@@ -23,14 +23,14 @@ class DashboardController < Dashboard::ApplicationController
   protected
 
   def load_events
-    project_ids =
+    projects =
       if params[:filter] == "starred"
         current_user.starred_projects
       else
         current_user.authorized_projects
-      end.pluck(:id)
+      end
 
-    @events = Event.in_projects(project_ids)
+    @events = Event.in_projects(projects)
     @events = @event_filter.apply_filter(@events).with_associations
     @events = @events.limit(20).offset(params[:offset] || 0)
   end

app/controllers/groups_controller.rb

@@ -89,10 +89,6 @@ class GroupsController < Groups::ApplicationController
     @projects ||= ProjectsFinder.new.execute(current_user, group: group).sorted_by_activity.non_archived
   end
 
-  def project_ids
-    @projects.pluck(:id)
-  end
-
   # Dont allow unauthorized access to group
   def authorize_read_group!
     unless @group and (@projects.present? or can?(current_user, :read_group, @group))
@@ -125,7 +121,7 @@ class GroupsController < Groups::ApplicationController
   end
 
   def load_events
-    @events = Event.in_projects(project_ids)
+    @events = Event.in_projects(@projects)
     @events = event_filter.apply_filter(@events).with_associations
     @events = @events.limit(20).offset(params[:offset] || 0)
   end

app/models/event.rb

@@ -47,7 +47,11 @@ class Event < ActiveRecord::Base
   # Scopes
   scope :recent, -> { reorder(id: :desc) }
   scope :code_push, -> { where(action: PUSHED) }
-  scope :in_projects, ->(project_ids) { where(project_id: project_ids).recent }
+
+  scope :in_projects, ->(projects) do
+    where(project_id: projects.select(:id).reorder(nil)).recent
+  end
+
   scope :with_associations, -> { includes(project: :namespace) }
   scope :for_milestone_id, ->(milestone_id) { where(target_type: "Milestone", target_id: milestone_id) }
 
@@ -64,12 +68,6 @@ class Event < ActiveRecord::Base
             [Event::CREATED, Event::CLOSED, Event::MERGED])
     end
 
-    def latest_update_time
-      row = select(:updated_at, :project_id).reorder(id: :desc).take
-
-      row ? row.updated_at : nil
-    end
-
     def limit_recent(limit = 20, offset = nil)
       recent.limit(limit).offset(offset)
     end

app/views/dashboard/projects/index.atom.builder

@@ -4,7 +4,7 @@ xml.feed "xmlns" => "http://www.w3.org/2005/Atom", "xmlns:media" => "http://sear
   xml.link    href: dashboard_projects_url(format: :atom, private_token: current_user.try(:private_token)), rel: "self", type: "application/atom+xml"
   xml.link    href: dashboard_projects_url, rel: "alternate", type: "text/html"
   xml.id      dashboard_projects_url
-  xml.updated @events.latest_update_time.xmlschema if @events.any?
+  xml.updated @events[0].updated_at.xmlschema if @events[0]
 
   @events.each do |event|
     event_to_atom(xml, event)

app/views/groups/show.atom.builder

@@ -4,7 +4,7 @@ xml.feed "xmlns" => "http://www.w3.org/2005/Atom", "xmlns:media" => "http://sear
   xml.link    href: group_url(@group, format: :atom, private_token: current_user.try(:private_token)), rel: "self", type: "application/atom+xml"
   xml.link    href: group_url(@group), rel: "alternate", type: "text/html"
   xml.id      group_url(@group)
-  xml.updated @events.latest_update_time.xmlschema if @events.any?
+  xml.updated @events[0].updated_at.xmlschema if @events[0]
 
   @events.each do |event|
     event_to_atom(xml, event)

app/views/projects/show.atom.builder

@@ -4,7 +4,7 @@ xml.feed "xmlns" => "http://www.w3.org/2005/Atom", "xmlns:media" => "http://sear
   xml.link    href: namespace_project_url(@project.namespace, @project, format: :atom, private_token: current_user.try(:private_token)), rel: "self", type: "application/atom+xml"
   xml.link    href: namespace_project_url(@project.namespace, @project), rel: "alternate", type: "text/html"
   xml.id      namespace_project_url(@project.namespace, @project)
-  xml.updated @events.latest_update_time.xmlschema if @events.any?
+  xml.updated @events[0].updated_at.xmlschema if @events[0?
 
   @events.each do |event|
     event_to_atom(xml, event)

app/views/users/show.atom.builder

@@ -4,7 +4,7 @@ xml.feed "xmlns" => "http://www.w3.org/2005/Atom", "xmlns:media" => "http://sear
   xml.link    href: user_url(@user, :atom), rel: "self", type: "application/atom+xml"
   xml.link    href: user_url(@user), rel: "alternate", type: "text/html"
   xml.id      user_url(@user)
-  xml.updated @events.latest_update_time.xmlschema if @events.any?
+  xml.updated @events[0].updated_at.xmlschema if @events[0]
 
   @events.each do |event|
     event_to_atom(xml, event)

spec/models/event_spec.rb

@@ -65,27 +65,6 @@ describe Event, models: true do
     it { expect(@event.author).to eq(@user) }
   end
 
-  describe '.latest_update_time' do
-    describe 'when events are present' do
-      let(:time) { Time.utc(2015, 1, 1) }
-
-      before do
-        create(:closed_issue_event, updated_at: time)
-        create(:closed_issue_event, updated_at: time + 5)
-      end
-
-      it 'returns the latest update time' do
-        expect(Event.latest_update_time).to eq(time + 5)
-      end
-    end
-
-    describe 'when no events exist' do
-      it 'returns nil' do
-        expect(Event.latest_update_time).to be_nil
-      end
-    end
-  end
-
   describe '.limit_recent' do
     let!(:event1) { create(:closed_issue_event) }
     let!(:event2) { create(:closed_issue_event) }