diff --git a/db/migrate/20200214022547_add_index_to_user_id_and_shixun_id_for_shixuns.rb b/db/migrate/20200214022547_add_index_to_user_id_and_shixun_id_for_shixuns.rb
new file mode 100644
index 000000000..0321d2c6b
--- /dev/null
+++ b/db/migrate/20200214022547_add_index_to_user_id_and_shixun_id_for_shixuns.rb
@@ -0,0 +1,14 @@
+class AddIndexToUserIdAndShixunIdForShixuns < ActiveRecord::Migration[5.2]
+  def change
+    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|
+      s = ShixunMember.where.not(id: sm.id).where(user_id: sm.user_id, shixun_id: sm.shixun_id)
+      puts "s: #{s.map{|sm| sm.id}}"
+      s.delete_all
+    end
+
+    add_index :shixun_members, [:user_id, :shixun_id], unique: true
+
+  end
+end