magento Bug with ressource collection - magento

Question

I noticed something strange in magento behavior.
it looks like either a bug, or i missed something...
I do a simple query to retreive products
$collection = Mage::getResourceModel('catalog/product_collection')
->addAttributeToSelect('price')
->addAttributeToSelect('sku')
->addAttributeToSelect('name')
->addAttributeToFilter(array(array(
'attribute' => 'my_attribute',
'eq' => 'my_value' )
));
//Then I update
foreach($collection as $_product){
$_product->setData("name","my_other_val");
$_product->save();
}
Magento will not only update "name", it will update ALL required fields and set the default value!!
So for instance, it changes the "visibility" attribute to "search, catalog" while the products were having another visibility!!
I have the mess now with my configurable products, and it changes also other attributes.
How do you explain this?
I did a reverse and the whole list of attributes is retrieved while saving the product, in this method:
walkAttributes
it does this:
case 'backend':
$instance = $attribute->getBackend();
Which retrieve ALL attributes. Since they have no value (they are not in the addAttributeToSelect section) then it uses the default value.
One soluton is to add
->addAttributeToSelect('visibility')
and all required attributes.
but too dangerous, I could miss one, or a new attribute could be added with the required attribute right?
For me it's a bug, because the default value should only apply to NON existing attribute value, but magento does not do a check, it does this query which either INSERT or UPDATE..
SQL: INSERT INTO catalog_product_entity_int (entity_type_id,attribute_id,store_id,entity_id,value) VALUES (?, ?, ?, ?, ?), (?, ?, ?, ?, ?), (?, ?, ?, ?, ?), (?, ?, ?, ?, ?) ON DUPLICATE KEY UPDATE value = VALUES(value)
...
Thanks,
Rod

Answer 1

This is not a bug. It's actually a feature. When loading a collection of products, not all attributes are loaded for the product, for performance reasons.
In order to be able to save it you need to call $product->load($id) and then $product->save().
Also you have to make sure that you are running your script under the store with id 0 (admin). The save works only for that. Add this at the top of your script
Mage::app()->setCurrentStore(Mage::getModel('core/store')->load(Mage_Core_Model_App::ADMIN_STORE_ID));
But here is an other idea. Don't use save. It's slow and you can do some damage if you are not careful. Use this instead.
Mage::getSingleton('catalog/product_action')->updateAttributes($productIds, $attributes, $storeId);
This works even if you are not on the admin store and it only changes the attributes you specify. This is what the parameters mean:
$productIds - an array with the product ids you need to change. array(12, 17, 219)
$attributes - an array with what you want to change array('name'=>'Your name here', 'description'=>'Your description here')
$storeId - the id of the store for which you do the change. Use 0 for default values.
Note: If you want to set different attribute values for different products you need to call this for each attribute value.
For example calling:
Mage::getSingleton('catalog/product_action')->updateAttributes(array(12, 17, 219), array('name'=>'Your name here'), 0);
will change the name for products with id 12,17 and 219

Answer 2

What you should do is update the product, from the collection result, after you load it explicitly.
Here's an example of what I mean:
$product_collection = Mage::getModel('catalog/product')
->getCollection()
->addAttributeToFilter(array(array(
'attribute' => 'my_attribute',
'eq' => 'my_value'
)));
foreach ($product_collection as $p) {
$product = Mage::getModel('catalog/product')->load(
$p->getId()
);
$product->setName('NEW NAME HERE');
try {
$product->save();
echo 'Product '. $product->getSku() .' has been updated.<br />';
} catch (Exception $e) {
echo 'Failed to update product '. $product->getSku() .' - '. $e->getMessage() .'<br />';
}
}
I am not saying this is the ONLY way to do this; however this works as intended.