迁移报错

db/migrate/20200313104522_add_total_duration_to_watch_course_duration.rb

@@ -1,6 +1,6 @@
 class AddTotalDurationToWatchCourseDuration < ActiveRecord::Migration[5.2]
   def change
-    add_column :watch_course_videos, :total_duration, :float, default: 0
+    #add_column :watch_course_videos, :total_duration, :float, default: 0
     WatchVideoHistory.where("created_at < '2020-03-14 00:00:00'").each do |d|
       d.watch_course_video.increment!(:total_duration, d.total_duration) if d.watch_course_video.present?
     end