You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: 20180103183451_add_missing_indexes.rb
    path of file: ./repos/forem/db/migrate
    
    the code of the file until where you have to start completion: class AddMissingIndexes < ActiveRecord::Migration[5.1]
  def change
    add_index :users, :username, unique: 
    
  def change
    add_index :users, :username, unique: true
    add_index :organizations, :slug, unique: true
    add_index :articles, :slug
    add_index :articles, :hotness_score
    add_index :articles, :featured_number
    add_index :articles, :published_at
  end