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db/migrate/20200214022547_add_index_to_user_id_and_shixun_id_for_shixuns.rb

@@ -3,7 +3,8 @@ class AddIndexToUserIdAndShixunIdForShixuns < ActiveRecord::Migration[5.2]
     shixun_members = ShixunMember.select("count(*) cnt, shixun_members.*").group(:user_id, :shixun_id).having("cnt > 1")
     puts "shixun_members: #{shixun_members.map{|sm| sm.id}}"
     shixun_members.each do |sm|
-      ShixunModify.find_by(id: sm.id).delete
+      s = ShixunModify.where.not(id: sm.id).where(user_id: sm.user_id, shixun_id: sm.shixun_id)
+      puts "s: #{s.map{|sm| sm.id}}"
     end
 
     add_index :shixun_members, [:user_id, :shixun_id], unique: true