Patch for nanosecond cache_key precision for Rails 3.x

cache_key_patch.rb

# see https://github.com/rails/rails/pull/6376

# put this in an initializer

module NsecCacheKeyPatch
  # Override ActiveRecord::Integration#cache_key

  def cache_key
    case
    when new_record?
      "#{self.class.model_name.cache_key}/new"
    when timestamp = self[:updated_at]
      timestamp = timestamp.utc.to_s(:nsec)
      "#{self.class.model_name.cache_key}/#{id}-#{timestamp}"
    else
      "#{self.class.model_name.cache_key}/#{id}"
    end
  end
end

::Time::DATE_FORMATS[:nsec] = '%Y%m%d%H%M%S%9N'

ActiveRecord::Base.send :include, NsecCacheKeyPatch