Remove N+1 query for tags in /admin/runners page

As discussed in https://github.com/mbleigh/acts-as-taggable-on/issues/91,
we can avoid N+1 queries if we use `tags` instead of `tag_list`.

Seen while reviewing
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19740.

1 files changed, 18 insertions, 1 deletions

diff --git a/spec/controllers/admin/runners_controller_spec.rb b/spec/controllers/admin/runners_controller_spec.rb
index 4cf14030ca1..82e24213408 100644
--- a/spec/controllers/admin/runners_controller_spec.rb
+++ b/spec/controllers/admin/runners_controller_spec.rb
@@ -1,18 +1,35 @@
 require 'spec_helper'
 
 describe Admin::RunnersController do
-  let(:runner) { create(:ci_runner) }
+  let!(:runner) { create(:ci_runner) }
 
   before do
     sign_in(create(:admin))
   end
 
   describe '#index' do
+    render_views
+
     it 'lists all runners' do
       get :index
 
       expect(response).to have_gitlab_http_status(200)
     end
+
+    it 'avoids N+1 queries', :request_store do
+      get :index
+
+      control_count = ActiveRecord::QueryRecorder.new { get :index }.count
+
+      create(:ci_runner, :tagged_only)
+
+      # There is still an N+1 query for `runner.builds.count`
+      expect { get :index }.not_to exceed_query_limit(control_count + 1)
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(response.body).to have_content('tag1')
+      expect(response.body).to have_content('tag2')
+    end
   end
 
   describe '#show' do