Merge branch 'feature/recent_order' into 'master'

'created_at DESC' is performed twice

If you are already sorting in descending order in the created_at, it is run twice when you run the .recent.

It has passed in the string 'created_at DESC'.
Ruby on Rails is directly given to the SQL.
It is a slow query in MySQL.

See merge request !825

CHANGELOG

@@ -32,6 +32,7 @@ v 7.13.0 (unreleased)
   - Better performance for pages with events list, issues list and commits list
   - Faster automerge check and merge itself when source and target branches are in same repository 
   - Correctly show anonymous authorized applications under Profile > Applications.
+  - Query Optimization in MySQL.
 
 v 7.12.1
   - Fix error when deleting a user who has projects (Stan Hu)

app/models/event.rb

@@ -44,7 +44,7 @@ class Event < ActiveRecord::Base
   after_create :reset_project_activity
 
   # Scopes
-  scope :recent, -> { order("created_at DESC") }
+  scope :recent, -> { order(created_at: :desc) }
   scope :code_push, -> { where(action: PUSHED) }
   scope :in_projects, ->(project_ids) { where(project_id: project_ids).recent }
   scope :with_associations, -> { includes(project: :namespace) }