Fixed bug:

- Migration gets executed unnecessarily on newly installed systems.
- Migration looks for `changed_at` column which should be `updated_at` instead.
- Migration removes `limit: 3` on `created_at` timestamp colums (MySQL millisecond support).

db/migrate/20150979000001_update_timestamps.rb

@@ -1,15 +1,18 @@
 class UpdateTimestamps < ActiveRecord::Migration[4.2]
   def up
+    # return if it's a new setup
+    return if !Setting.find_by(name: 'system_init_done')
+
     # get all models
     Models.all.each_value do |value|
       next if !value
       next if !value[:attributes]
 
-      if value[:attributes].include?('changed_at')
-        ActiveRecord::Migration.change_column value[:table].to_sym, :changed_at, :datetime, null: false
+      if value[:attributes].include?('updated_at')
+        ActiveRecord::Migration.change_column value[:table].to_sym, :updated_at, :datetime, limit: 3, null: false
       end
       if value[:attributes].include?('created_at')
-        ActiveRecord::Migration.change_column value[:table].to_sym, :created_at, :datetime, null: false
+        ActiveRecord::Migration.change_column value[:table].to_sym, :created_at, :datetime, limit: 3, null: false
       end
     end
   end