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: 20210225230057_create_chat_tables.rb
    path of file: ./repos/discourse/plugins/chat/db/migrate
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

class CreateChatTables < ActiveRecord::Migration[6.0]
  def change
    create_table :topic_chats do |t|
      t.in
    
  def change
    create_table :topic_chats do |t|
      t.integer :topic_id, null: false, index: true, unique: true
      t.datetime :deleted_at
      t.integer :deleted_by_id

      t.integer :featured_in_category_id
      t.integer :delete_after_seconds, default: nil
    end

    create_table :topic_chat_messages do |t|
      t.integer :topic_id, null: false
      t.integer :post_id, null: false, index: true
      t.integer :user_id, null: true
      t.timestamps
      t.datetime :deleted_at
      t.integer :deleted_by_id
      t.integer :in_reply_to_id, null: true
      t.text :message
    end

    add_index :topic_chat_messages, %i[topic_id created_at]
  end