Cache the number of open issues and merge requestscache-issue-and-mr-counts

Every project page displays a navigation menu that in turn displays the
number of open issues and merge requests. This means that for every
project page we run two COUNT(*) queries, each taking up roughly 30
milliseconds on GitLab.com. By caching these numbers and refreshing them
whenever necessary we can reduce loading times of all these pages by up
to roughly 60 milliseconds.

The number of open issues _includes_ confidential issues, even if you
can not see these issues. This is a trade-off to keep the code simple
and to ensure refreshing the data only needs 2 COUNT(*) queries instead
of 3. Further, by including all issues we don't need any additional work
to determine if the issue counter we display to a user should include
confidential issues or not. This does mean that if a project has 10
issues of which 5 are confidential, everybody (that can see the project)
will see the number 10.

Because we now have 3 similar counting service classes the code
previously used in Projects::ForksCountService has mostly been moved to
Projects::CountService, which in turn is reused by the various service
classes.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/36622

1 files changed, 5 insertions, 1 deletions

diff --git a/app/models/project.rb b/app/models/project.rb
index be248bc99e1..ddef8b82dee 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -1158,7 +1158,11 @@ class Project < ActiveRecord::Base
   end
 
   def open_issues_count
-    issues.opened.count
+    Projects::OpenIssuesCountService.new(self).count
+  end
+
+  def open_merge_requests_count
+    Projects::OpenMergeRequestsCountService.new(self).count
   end
 
   def visibility_level_allowed_as_fork?(level = self.visibility_level)