I'm trying to override the products collection that's coming from $this->getLoadedProductCollection() so I tried to override the method

class **_**_Model_Rewrite_Layer extends Mage_Catalog_Model_Layer {
  public function prepareProductCollection($collection) {
  $collection->addAttributeToFilter('my_attribute', array('in' => array(67)));

but that doesn't seem to work. When I add

echo ( $collection->getSelect() );

the query doesn't even include the layered navigation filters so I can't overwrite their logic.

What I'm trying to do is to change how one layered navigation filter works.

Am I on the right track to override prepareProductCollection() or should I go overriding a method that's called later in the process?

Any help would be appreciated.


I've solved that by rewriting the apply() method of the Mage_Catalog_Model_Layer_Filter_Attribute class.

At that place the attribute filter is added to the collection, bevore it is executed and you can do whatever you want. I.e. for filtering <= use:

$oAttributeModel = $this->getAttributeModel();
                            'lteq'  => $sFilterValue,
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  • Hey Tobias, thanks! I'm using Magento CE and the apply() method does look a little different for me. There's no attribute model available, or do I miss something? – oschloebe Apr 20 '13 at 13:14
  • The getAttributeModel method is available. Check the apply method on github github.com/magento/bugathon_march_2013/blob/master/app/code/… it calls ->_getRessource()->applyFilterToCollection($this ... In that applyFilterToCollection method github.com/magento/bugathon_march_2013/blob/master/app/code/… the getAttributeModel method is called on that $filter object. – Tobias Apr 20 '13 at 14:05
  • I see, thanks a lot! I think I managed to solve my problem; will post it in a minute hoping it will come in handy for others. Thanks Tobias! :) – oschloebe Apr 20 '13 at 14:45

Okay, thanks to Tobias Zander I managed to solve my problem. Dunno if this is the way to go, but it's doing what it should for me, so here's my solution on this:

1. In your existing module config.xml file add the following to the <global> scope:


2. Create a file in /app/code/local/YourCompany/YourModule/Catalog/Model/Resource/Layer/Filter/Attribute.php

3. Add the following to the newly created Attribute.php file:

class YourCompany_YourModule_Catalog_Model_Resource_Layer_Filter_Attribute extends Mage_Catalog_Model_Resource_Layer_Filter_Attribute {
public function applyFilterToCollection($filter, $value) {
    $collection = $filter->getLayer()->getProductCollection();
    $attribute  = $filter->getAttributeModel();
    $connection = $this->_getReadAdapter();
    $tableAlias = $attribute->getAttributeCode() . '_idx';

    $conditions = array(
        "{$tableAlias}.entity_id = e.entity_id",
        $connection->quoteInto("{$tableAlias}.attribute_id = ?", $attribute->getAttributeId()),
        $connection->quoteInto("{$tableAlias}.store_id = ?", $collection->getStoreId()),
        $connection->quoteInto("{$tableAlias}.value = ?", $value)

    if( $attribute->getAttributeCode() == 'my_attribute' ) { // Use another logic for your attribute only
        $value = 'x,y,z'; // Your logic goes here to add multiple values for the SQL IN() statement below
        $conditions[3] = $connection->quoteInto("{$tableAlias}.value IN($value)", $value);

        array($tableAlias => $this->getMainTable()),
        implode(' AND ', $conditions),

    return $this;

The only difference in my case is to use

$connection->quoteInto("{$tableAlias}.value IN($value)", $value)

instead of

$connection->quoteInto("{$tableAlias}.value = ?", $value)
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