Issue CSV preloads labels & author. Avoids N+1 queries.

app/views/projects/issues/index.csv.ruby

@@ -10,7 +10,7 @@ columns = {
   'Created At (UTC)' => -> (issue) { issue.created_at&.strftime('%Y-%m-%d %H:%M:%S') },
   'Updated At (UTC)' => -> (issue) { issue.updated_at&.strftime('%Y-%m-%d %H:%M:%S') },
   'Milestone' => -> (issue) { issue.milestone&.title },
-  'Labels' => -> (issue) { issue.label_names.join(',').presence },
+  'Labels' => -> (issue) { issue.labels_array.sort_by(&:title).map(&:title).join(',').presence },
 }
 
-CsvBuilder.new(columns).render(@issues)
+CsvBuilder.new(columns).render(@issues.includes(:author, :assignee, :labels))

spec/features/issues/csv_spec.rb

@@ -3,7 +3,10 @@ require 'spec_helper'
 describe 'Issues csv', feature: true do
   let(:user)    { create(:user) }
   let(:project) { create(:empty_project, :public) }
-  let!(:issue)  { create(:issue, project: project) }
+  let(:milestone) { create(:milestone, title: 'v1.0', project: project) }
+  let(:idea_label) { create(:label, project: project, title: 'Idea') }
+  let(:feature_label) { create(:label, project: project, title: 'Feature') }
+  let!(:issue)  { create(:issue, project: project, author: user) }
 
   before { login_as(user) }
 
@@ -15,7 +18,7 @@ describe 'Issues csv', feature: true do
   end
 
   it 'ignores pagination' do
-    create_list(:issue, 30, project: project)
+    create_list(:issue, 30, project: project, author: user)
 
     visit namespace_project_issues_path(project.namespace, project)
     click_on 'Download CSV'
@@ -30,11 +33,23 @@ describe 'Issues csv', feature: true do
     expect(csv.count).to eq 0
   end
 
-  context 'includes' do
-    let(:label1)    { create(:label, project: project, title: 'Feature') }
-    let(:label2)    { create(:label, project: project, title: 'labels') }
-    let(:milestone) { create(:milestone, title: "v1.0", project: project) }
+  def visit_project_csv
+    visit namespace_project_issues_path(project.namespace, project, format: :csv)
+  end
+
+  it 'avoids excessive database calls' do
+    control_count = ActiveRecord::QueryRecorder.new{ visit_project_csv }.count
+    create_list(:labeled_issue,
+                10,
+                project: project,
+                assignee: user,
+                author: user,
+                milestone: milestone,
+                labels: [feature_label, idea_label])
+    expect{ visit_project_csv }.not_to exceed_query_limit(control_count)
+  end
 
+  context 'includes' do
     before do
       issue.update!(milestone: milestone,
                     assignee: user,
@@ -42,9 +57,9 @@ describe 'Issues csv', feature: true do
                     due_date: DateTime.new(2014, 3, 2),
                     created_at: DateTime.new(2015, 4, 3, 2, 1, 0),
                     updated_at: DateTime.new(2016, 5, 4, 3, 2, 1),
-                    labels: [label1, label2])
+                    labels: [feature_label, idea_label])
 
-      visit namespace_project_issues_path(project.namespace, project, format: :csv)
+      visit_project_csv
     end
 
     specify 'title' do
@@ -72,14 +87,13 @@ describe 'Issues csv', feature: true do
     end
 
     specify 'labels' do
-      expect(csv[0]['Labels']).to eq 'Feature,labels'
+      expect(csv[0]['Labels']).to eq 'Feature,Idea'
     end
 
     specify 'due_date' do
       expect(csv[0]['Due Date']).to eq '2014-03-02'
     end
 
-
     specify 'created_at' do
       expect(csv[0]['Created At (UTC)']).to eq '2015-04-03 02:01:00'
     end
@@ -91,7 +105,7 @@ describe 'Issues csv', feature: true do
 
   context 'with minimal details' do
     it 'renders labels as nil' do
-      visit namespace_project_issues_path(project.namespace, project, format: :csv)
+      visit_project_csv
 
       expect(csv[0]['Labels']).to eq nil
     end