我想知道是否有任何方法来修改我的php代码，使之在数据库上更轻松一点？此代码在cronjob中每分钟运行一次。
希望确保这对db的影响尽可能小。

<?php
ini_set('memory_limit', '128M');
define('MAGENTO_ROOT', getcwd());
//exit;

$time     = time();
$time2    = $time - 0;
$to       = date('Y-m-d H:i:s', $time2);
$lastTime = $time - 60; //orders from the past X seconds
$from     = date('Y-m-d H:i:s', $lastTime);
$curDate  = date('Y-m-d');

$mageFilename = '/app/Mage.php';
require_once $mageFilename;
Mage::app();

$order_collection = Mage::getResourceModel('sales/order_collection');
$order_collection->addAttributeToSelect('*')->addAttributeToFilter('updated_at', array(
    'from' => $from,
    'to' => $to
))->getSelect();

print count($order_collection);
foreach ($order_collection->getItems() as $order) {
    $cards = Mage::getModel('giftcards/giftcards')->getCollection()->addFieldToFilter('order_id', $order->getId());
    print count($cards);
    foreach ($cards as $card) {
        if ($card->getCardStatus() == 0) {        
            if ((($card->getMailDeliveryDate() == null) || ($curDate == $card->getMailDeliveryDate())) && $card->getCardType() != 'offline') {
                $card->setCardStatus(1);
                $card->save();
                $card->send();
            }
        } elseif (($card->getCardStatus() == 1) && ($curDate < $card->getMailDeliveryDate())) {
            $card->setCardStatus(0);
            $card->save();
        }
    }
}
?>