Magento – Listing Random Products from all Subcategories of a Parent Category

blockscategorymagento-1.9product-listrandom

I need some help. I have the following category structure

category>subcagtegory>subsubcategory

The parent is an empty category that serves as a landing page. I need to display a list of random products from all the subcategories and subsubcategories on the parent landing category. Right now I have the following Random.php

class Mage_Catalog_Block_Product_List_Random extends Mage_Catalog_Block_Product_List
{
    protected function _getProductCollection()
    {
        if (is_null($this->_productCollection)) {
            $categoryID = $this->getCategoryId();
            if($categoryID)
            {
              $category = new Mage_Catalog_Model_Category();
              $category->load($categoryID);
              $collection = $category->getProductCollection();
            } else
            {
              $collection = Mage::getResourceModel('catalog/product_collection');
            }
            Mage::getModel('catalog/layer')->prepareProductCollection($collection);
            $collection->getSelect()->order('rand()');
            $collection->addStoreFilter();
            $numProducts = $this->getNumProducts() ? $this->getNumProducts() : 3;
            $collection->setPage(1, $numProducts)->load();

            $this->_productCollection = $collection;
        }
        return $this->_productCollection;
    }
}

and I call it on the parent's category "Custom Layout Update" like this:

<reference name="content">
     <block type="catalog/product_list_random" name="product.list.random" template="catalog/product/random.phtml">
        <action method="setCategoryId"><category_id>3</category_id></action>
        <action method="setColumnCount"><count>5</count></action>
        <action method="setNumProducts"><num_products>20</num_products></action>
    </block>
</reference>

What I need is to be able to specify a category ID in the XML just as I do now. But instead of listing products from one parent category (as it does now), I need to list products from all of its subcategories and subsubcategories. I believe I need an array of some sort but I am a PHP n00b so need help writing clean code.

Best Answer

Configure the parent category as anchor category. Anchor categories automatically include items from their subcategories.

On an unrelated note, ORDER BY RAND() is unperformant because it results in a resource intensive temp table copy. It has to load all results into a temporary table, assign a random number to each row and then sort without any index. Instead we retrieve all ids (this is faster and the amount of data is managable even for large catalogs), pick some randomly and retrieve these rows directly.

To do so, replace:

Mage::getModel('catalog/layer')->prepareProductCollection($collection);
$collection->getSelect()->order('rand()');
$collection->addStoreFilter();
$numProducts = $this->getNumProducts() ? $this->getNumProducts() : 3;
$collection->setPage(1, $numProducts)->load();

with:

$collection
    ->addStoreFilter()
    ->setVisibility(Mage::getSingleton('catalog/product_visibility')->getVisibleInCatalogIds());

$numberOfItems = $this->getNumProducts() ? $this->getNumProducts() : 3;
$candidateIds = $productCollection->getAllIds();

$choosenIds = [];
$maxKey = count($candidateIds)-1;
while (count($choosenIds) < $numberOfItems)) {
  $randomKey = mt_rand(0, $maxKey);
  $choosenIds[$randomKey] = $candidateIds[$randomKey];
}

$collection->addIdFilter($choosenIds);
$collection
    ->addMinimalPrice()
    ->addFinalPrice()
    ->addTaxPercents()
    ->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
    ->addUrlRewrite();

Related Solutions

Magento – Random products in product widget

The are two obvious approaches to achieve this. You can do it either within your theme or create a module that will utilise this functionality.

Within the theme you can just create a template (let's say in catalog/product/randomize.phtml) and put the following code in there:

$_category = Mage::getModel('catalog/category')->load($this->getCategoryId());
$productVisibility = Mage::getSingleton('catalog/product_visibility');
$_productCollection = Mage::getResourceModel('reports/product_collection')
                   ->addAttributeToSelect('*')
                   ->addStoreFilter()
                   ->addCategoryFilter($_category)
                   ->setVisibility($productVisibility->getVisibleInCatalogIds());
$_productCollection->getSelect()->order(new Zend_Db_Expr('RAND()'));                  
$_productCollection->setPage(1, 4);

and then in your CMS page you put something like this:

{{block type="core/template" name="whatever" template="catalog/product/randomize.phtml" category_id="YOUR_CATEGORY_ID"}}

The second approach is to create your module with just one block, extend Mage_Catalog_Block_Product_List and then implement _getProductCollection method in almost the same manner as in first approach:

protected function _getProductCollection()
{
    if (is_null($this->_productCollection)) {
        $_category = Mage::getModel('catalog/category')->load($this->getCategoryId());
        $productVisibility = Mage::getSingleton('catalog/product_visibility');
        $this->_productCollection = Mage::getResourceModel('reports/product_collection');
        $this->_productCollection->addAttributeToSelect('*')
            ->addStoreFilter()
            ->addCategoryFilter($_category)
            ->setVisibility($productVisibility->getVisibleInCatalogIds());
        $this->_productCollection->getSelect()->order(new Zend_Db_Expr('RAND()'));                  
        $this->_productCollection->setPage(1, 4);
    }

    return parent::_getProductCollection();
}

Then in your CMS page you can call your block like this:

{{block type="module_name/block_name" name="whatever" template="catalog/product/list.phtml" category_id="YOUR_CATEGORY_ID"}}

Magento – Display Random Products from Same Category with Parent Category Fill Up

I recently implemented something very similar and will share the relevant code below. But first some comments about performance, since that was the question:

General thoughts on performance for your requirements:

"they shouldn't be in cart" means, you have only limited means to cache the upsell block. I strongly recommend to do it anyway, but set cache key and cache lifetime only if the cart is empty.
Don't ORDER BY RAND() because it results in a resource intensive temp table copy. It has to load all results into a temporary table, assign a random number to each row and then sort without any index. Instead we retrieve all candidate ids (this is faster and the amount of data is managable even for large catalogs), pick some randomly and retrieve these rows directly. You can read about it in detail in my blog: http://www.schmengler-se.de/en/2015/09/show-random-products-in-magento-you-are-doing-it-wrong/

Specific performance problems with your solution

Don't use addAttributeToSelect('*') with EAV collections, only select what you need
Not entirely sure, but I doubt that new Zend_Db_Expr('FIELD(category_id, ' . implode(',', $_cat_order).')')) can efficiently use the MySQL indexes

Complete Solution

This is an observer for the catalog_product_upsell event. It uses the product collection provided by the product's category because I didn't need to fall back to the parent, but I'm sure you can adjust it.

use Mage_Catalog_Model_Product as Product;
use Mage_Catalog_Model_Product_Link as RelatedProduct;
use Mage_Catalog_Model_Resource_Product_Link_Product_Collection as RelatedProductCollection;

class IntegerNet_AutoUpsell_Model_Observer
{
    /**
     * @see event catalog_product_upsell
     * @param Varien_Event_Observer $observer
     * @throws Mage_Core_Exception
     */
    public function fillUpsellCollection(Varien_Event_Observer $observer)
    {
        $collection = $observer->getCollection();
        if ($collection instanceof RelatedProductCollection
            && $collection->getLinkModel()->getLinkTypeId() === RelatedProduct::LINK_TYPE_UPSELL
            && $collection->count() < $observer->getLimit('upsell')
        ) {
            $this->addItemsFromCategory($collection, $observer->getLimit('upsell') - $collection->count(), $observer->getProduct());
        }
    }
    protected function addItemsFromCategory(RelatedProductCollection $collection, $numberOfItems, Product $product)
    {
        /** @var Mage_Catalog_Model_Resource_Product_Collection $productsToAdd */
        $productsToAdd = $this->_getProductCategory($product)->getProductCollection();
        $productsToAdd
            ->addStoreFilter()
            ->addIdFilter(array_merge([$product->getId()], $collection->getAllIds()), true)
            ->setVisibility(Mage::getSingleton('catalog/product_visibility')->getVisibleInCatalogIds());

        $candidateIds = $productsToAdd->getAllIds();
        $choosenIds = [];
        $maxKey = count($candidateIds)-1;
        while (count($choosenIds) < $numberOfItems)) {
            $randomKey = mt_rand(0, $maxKey);
            $choosenIds[$randomKey] = $candidateIds[$randomKey];
        }    
        $productsToAdd
            ->addIdFilter($choosenIds)
            ->addMinimalPrice()
            ->addFinalPrice()
            ->addTaxPercents()
            ->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
            ->addUrlRewrite();
        foreach ($productsToAdd as $product) {
            $collection->addItem($product);
        }
    }

    /**
     * @param Mage_Catalog_Model_Product $product
     * @return Mage_Catalog_Model_Category
     */
    protected function _getProductCategory(Product $product)
    {
        $category = $product->getCategoryCollection()
            ->setPageSize(1)
            ->getFirstItem();
        return $category;
    }
}

Some parts that I'd like to highlight:

->addIdFilter(array_merge($product->getId(), $collection->getAllIds()), true)

This excludes the product itself and the products that are already manually defined as upsell products (I leave them and only fill the blanks with random products)

->addMinimalPrice()
->addFinalPrice()
->addTaxPercents()
->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
->addUrlRewrite();

This prepares the product collection to load the necessary data to display prices, the product link and any attributes configured as "used in product listing", but not more.