Magento doesn't use _beforeLoad events in collection function getAllIds

Question

I have an question about Magento that I don't know if is a bug or not.

Category Collection:

I used an Observer to filter only the customer categories (business rule)

My_Module/config.xml

<frontend>
        <events>
            <catalog_category_collection_load_before>
                <observers>
                    <my_module>
                        <type>model</type>
                        <class>my_module/catalog_observer</class>
                        <method>removeUnavailableCategories</method>
                    </my_module>
                </observers>
            </catalog_category_collection_load_before>
        </events>
</frontend>

My_Module/Model/Catalog/Observer.php

<?php
class My_Module_Model_Catalog_Observer
{
    function removeUnavailableCategories($observer)
    {
        $collection = $observer->getCategoryCollection();

        $allowedCategories = array();

         foreach (Mage::helper('my_module/customer')->getAllowedCategories() as $category)
         {
             $allowedCategories[]['like'] = $category->getPath();
             $allowedCategories[]['like'] = $category->getPath() . '/%';
         }

        if (count($allowedCategories) > 0)
        {
            $collection->addFieldToFilter('path', $allowedCategories);
        }
        else
        {
            /**
             * Clear collection
             */
            $collection->getSelect()->reset(Zend_Db_Select::WHERE);
            $collection->getSelect()->where('e.entity_id < 0');
        }
    }
}

As you can see, I put a filter to show only the categories allowed for the customer.

But, when I use the function "getAllIds" in the category collection, this observer is not called:

Mage::getModel('catalog/category')->getCollection()->getAllIds();

I do it like this:

Mage::getModel('catalog/category')->getCollection()->load()->getAllIds();

And it worked.

But I don't like this. Since the function "getAllIds" makes the search again:

Mage_Eav_Model_Entity_Collection_Abstract

protected function _getAllIdsSelect($limit = null, $offset = null)
{
    $idsSelect = clone $this->getSelect();
    $idsSelect->reset(Zend_Db_Select::ORDER);
    $idsSelect->reset(Zend_Db_Select::LIMIT_COUNT);
    $idsSelect->reset(Zend_Db_Select::LIMIT_OFFSET);
    $idsSelect->reset(Zend_Db_Select::COLUMNS);
    $idsSelect->columns('e.' . $this->getEntity()->getIdFieldName());
    $idsSelect->limit($limit, $offset);

    return $idsSelect;
}

public function getAllIds($limit = null, $offset = null)
{
    return $this->getConnection()->fetchCol($this->_getAllIdsSelect($limit, $offset), $this->_bindParams);
}

My question is:

Is it correct use to call the function _beforeLoad before search for the IDs?

Like this:

public function getAllIds($limit = null, $offset = null)
{
    $this->_beforeLoad();
    return $this->getConnection()->fetchCol($this->_getAllIdsSelect($limit, $offset), $this->_bindParams);
}

OR

protected function _getAllIdsSelect($limit = null, $offset = null)
{
    $this->_beforeLoad();

    $idsSelect = clone $this->getSelect();
    $idsSelect->reset(Zend_Db_Select::ORDER);
    $idsSelect->reset(Zend_Db_Select::LIMIT_COUNT);
    $idsSelect->reset(Zend_Db_Select::LIMIT_OFFSET);
    $idsSelect->reset(Zend_Db_Select::COLUMNS);
    $idsSelect->columns('e.' . $this->getEntity()->getIdFieldName());
    $idsSelect->limit($limit, $offset);

    return $idsSelect;
}

Or is there something that I don't know?

Answer 1

It's intended behavior. getAllIds() is meant to be used for a single COUNT() query and does not actually load the collection. So triggering the before_load event does not make sense semantically.

I would not recommend to rewrite the category model to always call _beforeLoad() as you suggested because that might result in undesired side effects.

On the other hand I understand why you'd want it because most of the time you change filters in this event and having those on the count query would be useful.

A possible solution is to move the actual filter logic from the observer to a different class (could be a helper) and call it from the observer and also in the places where you use getAllIds() in your code.