优化数据迁移效率

db/migrate/20141229025925_change_seems_rateable_rates.rb

@@ -1,23 +1,27 @@
 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
-          teachers = []
-          course.members.each do |m|
-            teachers << m.user_id  if m && m.user && m.user.allowed_to?(:as_teacher,course)
-          end
-          if teachers.include?(rate.rater_id)
-            rate.is_teacher_score = 1
-            rate.save
+      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
+              end
+            end
           end
         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