Load out-of-stock products after the in-stock products in the category listing

Question

I want to show first all in-stock products and then out-of-stock products respectively and sort by price in the ascending order.

Following is my code. In my local.xml I wrote the following code for the price from low to high

<catalog_category_layered>
        <reference name="product_list">
            <action method="setDefaultDirection"><dir>asc</dir></action>
        </reference>
    </catalog_category_layered>

and I wrote an observer to show all out-of-stock products last, i.e., after loading all in-stock products. For this I had used the catalog_product_collection_load_before event

$collection = $observer->getCollection();
        $collection->getSelect()->joinLeft(
            array('_inventory_table'=>$collection->getTable('cataloginventory/stock_item')),
            "_inventory_table.product_id = e.entity_id",
            array('is_in_stock', 'manage_stock')
        );
        $collection->addExpressionAttributeToSelect(
            'on_top',
            '(CASE WHEN (((_inventory_table.use_config_manage_stock = 1) AND (_inventory_table.is_in_stock = 1)) OR  ((_inventory_table.use_config_manage_stock = 0) AND (1 - _inventory_table.manage_stock + _inventory_table.is_in_stock >= 1))) THEN 1 ELSE 0 END)',
            array()
        );
        $collection->getSelect()->order('on_top DESC');
        $order = $collection->getSelect()->getPart('order');
        array_unshift($order, array_pop($order));
        $collection->getSelect()->setPart('order', $order);

Now what is happening is I can see the products from low to high but not out-of-stock products last.

Answer 1

Use

Mage::getResourceModel('cataloginventory/stock_status')
    ->addStockStatusToSelect($select, Mage::app()->getWebsite());`

And then sort by salable desc

Answer 2

you have to use another event, catalog_product_collection_load_before is useless because Mage_Review Module-Observer loads the product list collection so you cant edit this collection any more. You can disable this observer if you dont use reviews or do it like described here:

catalog_product_collection_load_before and getLoadedProductCollection

Regards