create_table "delayed_jobs", :force => true do |t|
    t.integer  "priority",   :default => 0
    t.integer  "attempts",   :default => 0
    t.text     "handler"
    t.text     "last_error"
    t.datetime "run_at"
    t.datetime "locked_at"
    t.datetime "failed_at"
    t.string   "locked_by"
    t.string   "queue"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

> TINYTEXT  256 bytes     TEXT  65,535 bytes     MEDIUMTEXT  16,777,215 bytes
> LONGTEXT  4,294,967,295 bytes

create_table :messages do |t|
  t.string :body,
......
end

def up
  change_table :messages do |t|
    t.change :body, :text
  end
end