数据迁移

db/migrate/20160513120002_delete_empty_apply_homework.rb

@@ -4,8 +4,8 @@ class DeleteEmptyApplyHomework < ActiveRecord::Migration
     transaction do
       for i in 1 ... count do i
         ApplyHomework.page(i).per(30).each do |ah|
-          homework = HomeworkCommon.find ah.homework_common_id
+          homework = HomeworkCommon.where("id = ?",ah.homework_common_id)
-          if homework.nil?
+          if homework.empty?
             ah.destroy
           end
         end