Merge pull request #5380 from opf/fix/increase_cf_timestamp_migration_robustness

increase custom field timestamp migration robustness

db/migrate/20170418064453_add_timestamp_to_custom_fields.rb

@@ -1,9 +1,17 @@
 class AddTimestampToCustomFields < ActiveRecord::Migration[5.0]
-  def change
-    add_column :custom_fields, :created_at, :datetime
-    add_column :custom_fields, :updated_at, :datetime
+  def up
+    add_column :custom_fields, :created_at, :datetime unless column_exists? :custom_fields, :created_at
+    add_column :custom_fields, :updated_at, :datetime unless column_exists? :custom_fields, :updated_at
 
-    add_column :custom_options, :updated_at, :datetime
-    add_column :custom_options, :created_at, :datetime
+    add_column :custom_options, :created_at, :datetime unless column_exists? :custom_options, :created_at
+    add_column :custom_options, :updated_at, :datetime unless column_exists? :custom_options, :updated_at
+  end
+
+  def down
+    remove_column :custom_fields, :created_at, :datetime
+    remove_column :custom_fields, :updated_at, :datetime
+
+    remove_column :custom_options, :created_at, :datetime
+    remove_column :custom_options, :updated_at, :datetime
   end
 end