redmine/db/migrate/20091017213027_add_missing_indexes_to_comments.rb

class AddMissingIndexesToComments < ActiveRecord::Migration[4.2]
  def self.up
    add_index :comments, [:commented_id, :commented_type]
    add_index :comments, :author_id
  end

  def self.down
    remove_index :comments, :column => [:commented_id, :commented_type]
    remove_index :comments, :author_id
  end
end