Merge branch 'bw-reference-user-caching' into 'master'

Check for N+1 in UserReferenceFilter

See merge request gitlab-org/gitlab!61514

spec/lib/banzai/filter/references/user_reference_filter_spec.rb

@@ -201,4 +201,25 @@ RSpec.describe Banzai::Filter::References::UserReferenceFilter do
       expect(filter.send(:usernames)).to eq([user.username])
     end
   end
+
+  context 'checking N+1' do
+    let(:user2)      { create(:user) }
+    let(:group)      { create(:group) }
+    let(:reference2) { user2.to_reference }
+    let(:reference3) { group.to_reference }
+
+    it 'does not have N+1 per multiple user references', :use_sql_query_cache do
+      markdown = "#{reference}"
+
+      control_count = ActiveRecord::QueryRecorder.new(skip_cached: false) do
+        reference_filter(markdown)
+      end.count
+
+      markdown = "#{reference} @qwertyuiopzx @wertyuio @ertyu @rtyui #{reference2} #{reference3}"
+
+      expect do
+        reference_filter(markdown)
+      end.not_to exceed_all_query_limit(control_count)
+    end
+  end
 end