Implement review comments from @yorickpeterse

1. Change multiple updates to a single `update_all`

2. Use cascading deletes

3. Extract an average function for the database median.

4. Move database median to `lib/gitlab/database`

5. Use `delete_all` instead of `destroy_all`

6. Minor refactoring

1 files changed, 0 insertions, 12 deletions

diff --git a/app/models/merge_request/metrics.rb b/app/models/merge_request/metrics.rb
index 8c42c830fac..697a2e303fb 100644
--- a/app/models/merge_request/metrics.rb
+++ b/app/models/merge_request/metrics.rb
@@ -8,16 +8,4 @@ class MergeRequest::Metrics < ActiveRecord::Base
 
     self.save if self.changed?
   end
-
-  def record_production_deploy!(deploy_time)
-    self.update(first_deployed_to_production_at: deploy_time) if self.first_deployed_to_production_at.blank?
-  end
-
-  def record_latest_build_start_time!(start_time)
-    self.update(latest_build_started_at: start_time, latest_build_finished_at: nil)
-  end
-
-  def record_latest_build_finish_time!(finish_time)
-    self.update(latest_build_finished_at: finish_time)
-  end
 end