diff --git a/db/migrate/20191203032557_add_uniq_index_to_exercise_answer.rb b/db/migrate/20191203032557_add_uniq_index_to_exercise_answer.rb
index ca38fab23..b46ff0e34 100644
--- a/db/migrate/20191203032557_add_uniq_index_to_exercise_answer.rb
+++ b/db/migrate/20191203032557_add_uniq_index_to_exercise_answer.rb
@@ -1,9 +1,9 @@
 class AddUniqIndexToExerciseAnswer < ActiveRecord::Migration[5.2]
   def change
-    remove_index :exercise_answers, column: [:exercise_question_id, :user_id]
-
-    change_column_default :exercise_answers, :exercise_choice_id, from: nil, to: -1
-    ExerciseAnswer.where(exercise_choice_id: nil).update_all(exercise_choice_id: -1)
+    # remove_index :exercise_answers, column: [:exercise_question_id, :user_id]
+    #
+    # change_column_default :exercise_answers, :exercise_choice_id, from: nil, to: -1
+    # ExerciseAnswer.where(exercise_choice_id: nil).update_all(exercise_choice_id: -1)
 
     sql = %Q(delete from exercise_answers where (exercise_question_id, user_id, exercise_choice_id) in
             (select * from (select exercise_question_id, user_id, exercise_choice_id from exercise_answers group by exercise_question_id, user_id, exercise_choice_id having count(*) > 1) a)