Cache the number of forks of a projectforks-count-cache

The number of forks of a project doesn't change very frequently and
running a COUNT(*) every time this information is requested can be quite
expensive. We also end up running such a COUNT(*) query at least twice
on the homepage of a project.

By caching this data and refreshing it when necessary we can reduce
project homepage loading times by around 60 milliseconds (based on the
timings of https://gitlab.com/gitlab-org/gitlab-ce).

1 files changed, 10 insertions, 0 deletions

diff --git a/spec/models/project_spec.rb b/spec/models/project_spec.rb
index d9ab44dc49f..eba71ba2f72 100644
--- a/spec/models/project_spec.rb
+++ b/spec/models/project_spec.rb
@@ -2310,4 +2310,14 @@ describe Project do
       end
     end
   end
+
+  describe '#forks_count' do
+    it 'returns the number of forks' do
+      project = build(:project)
+
+      allow(project.forks).to receive(:count).and_return(1)
+
+      expect(project.forks_count).to eq(1)
+    end
+  end
 end