Reduce N+1 from Activity Dashboard and Banzaifix-n-plus-1-queries-projects

There is a combination of few strategies implemented here:

1. Few relations were eager loaded
2. Changed few polymorphic routes to specific ones so we don't have to
   use `#becomes(Namespace)` which doesn't preserve association cache

5 files changed, 15 insertions, 3 deletions

diff --git a/app/helpers/events_helper.rb b/app/helpers/events_helper.rb
index 3ce2398f1de..d5a2aa0231f 100644
--- a/app/helpers/events_helper.rb
+++ b/app/helpers/events_helper.rb
@@ -161,6 +161,12 @@ module EventsHelper
       project_commit_url(event.project, event.note_target, anchor: dom_id(event.target))
     elsif event.project_snippet_note?
       project_snippet_url(event.project, event.note_target, anchor: dom_id(event.target))
+    elsif event.issue_note?
+      namespace_project_issue_url(namespace_id: event.project.namespace_id, project_id: event.project_id,
+                                  id: event.note_target, anchor: dom_id(event.target))
+    elsif event.merge_request_note?
+      namespace_project_merge_request_url(namespace_id: event.project.namespace_id, project_id: event.project_id,
+                                          id: event.note_target, anchor: dom_id(event.target))
     else
       polymorphic_url([event.project.namespace.becomes(Namespace),
                        event.project, event.note_target],
diff --git a/app/helpers/projects_helper.rb b/app/helpers/projects_helper.rb
index 0a7f930110a..878dc01074b 100644
--- a/app/helpers/projects_helper.rb
+++ b/app/helpers/projects_helper.rb
@@ -2,7 +2,7 @@
 
 module ProjectsHelper
   def link_to_project(project)
-    link_to [project.namespace.becomes(Namespace), project], title: h(project.name) do
+    link_to admin_namespace_project_path(namespace_id: project.namespace_id, id: project), title: h(project.name) do
       title = content_tag(:span, project.name, class: 'project-name')
 
       if project.namespace
diff --git a/app/models/event.rb b/app/models/event.rb
index 2e690f8c013..2ceef412af5 100644
--- a/app/models/event.rb
+++ b/app/models/event.rb
@@ -87,7 +87,7 @@ class Event < ActiveRecord::Base
   scope :with_associations, -> do
     # We're using preload for "push_event_payload" as otherwise the association
     # is not always available (depending on the query being built).
-    includes(:author, :project, project: :namespace)
+    includes(:author, :project, project: [:project_feature, :import_data, :namespace])
       .preload(:target, :push_event_payload)
   end
 
diff --git a/app/models/note.rb b/app/models/note.rb
index 592efb714f3..c2fdddd8b7c 100644
--- a/app/models/note.rb
+++ b/app/models/note.rb
@@ -131,7 +131,7 @@ class Note < ActiveRecord::Base
   scope :with_associations, -> do
     # FYI noteable cannot be loaded for LegacyDiffNote for commits
     includes(:author, :noteable, :updated_by,
-             project: [:project_members, { group: [:group_members] }])
+             project: [:project_members, :namespace, { group: [:group_members] }])
   end
   scope :with_metadata, -> { includes(:system_note_metadata) }
 
diff --git a/changelogs/unreleased/fix-n-plus-1-queries-projects.yml b/changelogs/unreleased/fix-n-plus-1-queries-projects.yml
new file mode 100644
index 00000000000..cb625784267
--- /dev/null
+++ b/changelogs/unreleased/fix-n-plus-1-queries-projects.yml
@@ -0,0 +1,6 @@
+---
+title: Fix some N+1 queries related to Admin Dashboard, User Dashboards and Activity
+  Stream
+merge_request: 23034
+author:
+type: performance