Apply filter on collection Object

I am getting this object on list page

$_productCollection=$this->getLoadedProductCollection();

//return 3 records

now I applied filter as

$_productCollection=$_productCollection->addFieldToFilter('genre', array('finset' => '126'));

//now it should return 1 record

but it gives me a 开发者_开发技巧count of 3. Now, if I run the query in database by getting the query using echo $_productCollection->getSelect(); it returns 1 record.

Can anybody help me to resolve this?

Most likely this doesn't work because $this->getLoadedProductCollection() returns a collection which already has been loaded by the catalog/layer singleton.

But you could override Mage_Catalog_Model_Layer::prepareProductCollection() to get in control and add the custom filters you want.