Remove repeated query for merge requests discussion collectionissue_27166

2 files changed, 19 insertions, 10 deletions

diff --git a/app/models/note.rb b/app/models/note.rb
index 832c68243fb..115a2775ffb 100644
--- a/app/models/note.rb
+++ b/app/models/note.rb
@@ -249,7 +249,7 @@ class Note < ActiveRecord::Base
     # When commit notes are rendered on an MR's Discussion page, they are
     # displayed in one discussion instead of individually.
     # See also `#discussion_id` and `Discussion.override_discussion_id`.
-    if noteable && noteable != self.noteable
+    if different_context?(noteable)
       OutOfContextDiscussion
     else
       IndividualNoteDiscussion
@@ -300,6 +300,12 @@ class Note < ActiveRecord::Base
 
   private
 
+  def different_context?(noteable)
+    return false unless noteable
+
+    noteable.id != noteable_id && noteable.class.name != noteable_type
+  end
+
   def keep_around_commit
     project.repository.keep_around(self.commit_id)
   end
diff --git a/spec/features/merge_requests/discussion_spec.rb b/spec/features/merge_requests/discussion_spec.rb
index 1a09cc54c2e..b2b133b0466 100644
--- a/spec/features/merge_requests/discussion_spec.rb
+++ b/spec/features/merge_requests/discussion_spec.rb
@@ -24,23 +24,26 @@ feature 'Merge Request Discussions', feature: true do
       )
     end
 
-    let(:outdated_diff_refs) { project.commit("874797c3a73b60d2187ed6e2fcabd289ff75171e").diff_refs }
-
-    before(:each) do
+    def visit_merge_request
       visit namespace_project_merge_request_path(project.namespace, project, merge_request)
     end
 
-    context 'active discussions' do
-      it 'shows a link to the diff' do
-        within(".discussion[data-discussion-id='#{active_discussion.id}']") do
-          path = diffs_namespace_project_merge_request_path(project.namespace, project, merge_request, anchor: active_discussion.line_code)
-          expect(page).to have_link('the diff', href: path)
-        end
+    let(:outdated_diff_refs) { project.commit("874797c3a73b60d2187ed6e2fcabd289ff75171e").diff_refs }
+
+    it "avoids repeated database queries" do
+      control_count = ActiveRecord::QueryRecorder.new { visit_merge_request }.count
+
+      5.times do
+        create(:diff_note_on_merge_request, noteable: merge_request, project: project).to_discussion
       end
+
+      expect { visit_merge_request }.not_to exceed_query_limit(control_count)
     end
 
     context 'outdated discussions' do
       it 'shows a link to the outdated diff' do
+        visit_merge_request
+
         within(".discussion[data-discussion-id='#{outdated_discussion.id}']") do
           path = diffs_namespace_project_merge_request_path(project.namespace, project, merge_request, diff_id: old_merge_request_diff.id, anchor: outdated_discussion.line_code)
           expect(page).to have_link('an old version of the diff', href: path)