db/migrate/050_add_user_index_to_diary_comments.rb

   1 class AddUserIndexToDiaryComments < ActiveRecord::Migration[5.0]
   2   def self.up
   3     add_index :diary_comments, [:user_id, :created_at], :name => "diary_comment_user_id_created_at_index"
   4   end
   5
   6   def self.down
   7     remove_index :diary_comments, :name => "diary_comment_user_id_created_at_index"
   8   end
   9 end