.map -> .pluck

app/models/milestone.rb

@@ -11,7 +11,7 @@ class Milestone < ActiveRecord::Base
   end
 
   def participants
-    User.where(id: issues.map(&:assignee_id))
+    User.where(id: issues.pluck(:assignee_id))
   end
 
   def percent_complete

app/models/project.rb

@@ -147,7 +147,7 @@ class Project < ActiveRecord::Base
   end
 
   def wiki_notes
-    Note.where(noteable_id: wikis.map(&:id), noteable_type: 'Wiki', project_id: self.id)
+    Note.where(noteable_id: wikis.pluck(:id), noteable_type: 'Wiki', project_id: self.id)
   end
 
   def project_id