Use Atom update times of the first eventevents-performance

By simply loading the first event from the already sorted set we save
ourselves extra (slow) queries just to get the latest update timestamp.
This removes the need for Event.latest_update_time and significantly
reduces the time needed to build an Atom feed.

Fixes gitlab-org/gitlab-ce#12415

1 files changed, 1 insertions, 7 deletions

diff --git a/app/models/event.rb b/app/models/event.rb
index 8dfc1d04709..4be23a1cf72 100644
--- a/app/models/event.rb
+++ b/app/models/event.rb
@@ -49,7 +49,7 @@ class Event < ActiveRecord::Base
   scope :code_push, -> { where(action: PUSHED) }
 
   scope :in_projects, ->(projects) do
-    where(project_id: projects.reorder(nil).id_only).recent
+    where(project_id: projects.select(:id).reorder(nil)).recent
   end
 
   scope :with_associations, -> { includes(project: :namespace) }
@@ -68,12 +68,6 @@ class Event < ActiveRecord::Base
             [Event::CREATED, Event::CLOSED, Event::MERGED])
     end
 
-    def latest_update_time
-      row = select(:updated_at, :project_id).reorder(id: :desc).take
-
-      row ? row.updated_at : nil
-    end
-
     def limit_recent(limit = 20, offset = nil)
       recent.limit(limit).offset(offset)
     end