gistfile1.txt

    public function qoaKeyName ()
    {
      return 'quantity_on_orders_' . $this->id();
    }

    /**
     * Quantity of this part's storefront product available for sale to the general public.
     */
    public function quantityForSale ()
    {
      if (MEMCACHED_ENABLED === true) {
        $cache = SparkCache::getInstance();

        if (! $quantity = $cache->get($this->qoaKayName())) {
          $quantity = $this->StorefrontProduct->products_physical_quantity
                    - $this->quantityOnOrders()
                    - $this->reservedQuantity();

          $cache->set($this->qoaKeyName(), $quantity);
        }
      }
      else {
        $quantity = $this->StorefrontProduct->products_physical_quantity
                  - $this->quantityOnOrders()
                  - $this->reservedQuantity();
      }

      return $quantity;
    }