Magento: Getting a shipment collection containing only shipments that contain a comment that contains a certain piece of text

I need to query for a collection of order shipments (Mage_Sales_Model_Mysql4_Order_Shipment_Collection). I only want to see the order shipment on which a comment has been written that matches a certain piece of text.

In non-EAV SQL, it would l开发者_运维百科ook something like this:

SELECT shipments.id
FROM shipments
JOIN comments ON (
    shipments.id = comments.shipment_id
    AND comments.content IN('Possible comment', 'Another possible comment')
    )
GROUP BY shipments.id

Obviously I want to use Magento's native model methods to accomplish it:

$shipments = Mage::getResourceModel('sales/order_shipment_collection')
    ->addAttributeToSelect('*')
    // ??
    // ??
    ->load();

Is this possible?

---

To keep things neat I would put the following inside my own resource model which extends Mage_Sales_Model_Mysql4_Order_Shipment_Collection.

public function addCommentsToFilter($comments = array())
{
    return $this->join('sales/shipment_comment', 'main_table.entity_id=parent_id', 'comment')
        ->addFieldToFilter('comment', array('in'=>$comments));
}

Then call it with:

$shipments = Mage::getResourceModel('mymodule/my_custom_collection')
    ->addAttributeToSelect('*')
    ->addCommentsToFilter(array('Possible comment', 'Another possible comment'));