Catalog Advanced Search - Multiple Sort

Question

I'm trying to sort Advanced Search result by Order parameter and Price.

Eg:

User sorts results by Manufacturer, direction DESC from toolbar. In this case I need to order by manufaturer DESC then by price ASC.

I have created an Observer that Observs catalog_block_product_list_collection

This is my module Observer.php function:

public function catalog_block_product_list_collection(Varien_Event_Observer $observer)
{
   $collection = $observer->getEvent()->getCollection(); 
   $collection->getSelect()->order('price','ASC'); 
   /*OR $collection->addOrder('price',Varien_Data_Collection::SORT_ORDER_DESC);*/       
   return $this;
} 

But result list is sorted by Manufacturer only.

If I print $collection->getSelect()->__toString(); in mynamespace/mymodule/catalog/product/list.phtml i see that order is set correctly

ORDER BY `manufacturer` DESC, `price` ASC LIMIT 20

Query execution from MySQL returns the expeted result, Magento don't.

What's wrong with my code?

Is it possible to do what I'm trying to do ?

EDIT [SOLUTION]

After googling a while and a day of trying i solved my problem. Here is the code:

/**
 * @param Varien_Event_Observer $observer
 * @return Spm_Sorter_Model_Observer
 */
public function catalog_block_product_list_collection(Varien_Event_Observer $observer)
{
    // Get && Clear Collection
    $collection = $observer->getEvent()->getCollection();
    $collection->clear();

    // get current Sort && Direction
    $currSortOrder     = Mage::getBlockSingleton('catalog/product_list_toolbar')->getCurrentOrder();
    $currSortDirection = Mage::getBlockSingleton('catalog/product_list_toolbar')->getCurrentDirection();

    // If is current Sort is price || special price need some special stuff
    if(in_array($currSortOrder,['price','special_price'])){

        // Rest collection sort
        $collection->getSelect()->reset(Zend_Db_Select::ORDER);

        /**
         * Set Special Price order Index.
         * Discounted products must be at the top of the list
         * This 'index' is needed because of :
         *  ORDER BY special_price  -> products with no discount comes first, they have NULL value
         *                             If special price is out of date range we will have wrong order to, 
         *                             special price is valued but not valid.              
         *  ORDER BY min_price      -> products with no discount but price lower than discounted ones comes first
         * */
        $collection->getSelect()->columns(
            array(
                'special_price_index' => new Zend_Db_Expr('IF(`price_index`.`price` <> `price_index`.`min_price`,`price_index`.`price`, 99999)')
            )
        );

        //  Set special price sort. Direction ASC if current order != pecial_price, current otherwise
        $collection->getSelect()->order('special_price_index',($currSortOrder === 'special_price' ? $currSortDirection : Varien_Data_Collection::SORT_ORDER_ASC));
    }

    //  Set price sort. Direction ASC if current order != price, current otherwise
    $collection->setOrder('price',($currSortOrder === 'price' ?  $currSortDirection : Varien_Data_Collection::SORT_ORDER_ASC));

    return $this;
}

Answer 1

This issue occurs because after your statement another statement running for fetch record in Magento.

The problem is that $collection is loaded somewhere before our observer. $collection->clear(); clear collection

Thanks