迁移调整

db/migrate/20191203124938_add_index_to_poll_answer.rb

@@ -1,6 +1,8 @@
 class AddIndexToPollAnswer < ActiveRecord::Migration[5.2]
   def change
-    remove_index :poll_votes, column: [:poll_question_id, :user_id]
+    remove_index :poll_votes, :poll_question_id
+    remove_index :poll_votes, :user_id
+    remove_index :poll_votes, :poll_answer_id
 
     change_column_default :poll_votes, :poll_question_id, from: nil, to: -1
     PollVote.where(poll_answer_id: nil).update_all(poll_answer_id: -1)