Use Iterator to mass update products for performance optimization

fastproductupdate.php

// Get Collection
$collection = Mage::getModel('catalog/product')->getCollection()
    ->addAttributeToSelect('sku')
    ->addAttributeToSelect('publihser')
    ->addFieldToFilter(array(array('attribute'=>'publisher','eq'=>$publisher)));

function productUpdateCallback($args){
    $product = Mage::getModel('catalog/product');
    $product->setData($args['row']);
    $productId = $product->getId();
    $sku = 'yourSku';

    // Updates a single attribute, much faster than calling a full product save
    Mage::getSingleton('catalog/product_action')
        ->updateAttributes(array($productId), array('sku' => $sku), 0);
}

// Walk through collection, for large collections this is much faster than using foreach
Mage::getSingleton('core/resource_iterator')->walk($collection->getSelect(), array('productUpdateCallback'));