修改字段类型为longtext

db/migrate/20170330084904_change_type_to_chanllenge.rb

@@ -0,0 +1,9 @@
+class ChangeTypeToChanllenge < ActiveRecord::Migration
+  def up
+    change_column :challenges, :task_pass, :longtext
+    change_column :challenges, :answer, :longtext
+  end
+
+  def down
+  end
+end