优化数据迁移效率

db/migrate/20141229025925_change_seems_rateable_rates.rb

@@ -1,14 +1,13 @@
 class ChangeSeemsRateableRates < ActiveRecord::Migration
   def up
-    SeemsRateableRates.where("rateable_type = 'HomeworkAttach'").each do |rate|
-      homework = HomeworkAttach.find_by_id rate.rateable_id
-      if homework
-        course = homework.bid.courses.first
-        if course
+      Course.all.each do |course|
         teachers = []
         course.members.each do |m|
           teachers << m.user_id  if m && m.user && m.user.allowed_to?(:as_teacher,course)
         end
+        course.homeworks.each do |bid|
+          bid.homeworks.each do |homework|
+            SeemsRateableRates.where("rateable_type = 'HomeworkAttach' and rateable_id = #{homework.id}").each do |rate|
               if teachers.include?(rate.rater_id)
                 rate.is_teacher_score = 1
                 rate.save
@@ -17,7 +16,12 @@ class ChangeSeemsRateableRates < ActiveRecord::Migration
           end
         end
       end
+  end
 
   def down
+    SeemsRateableRates.where("is_teacher_score = 1").each do |rate|
+      rate.is_teacher_score = 0
+      rate.save
+    end
   end
 end