magento get products from category, order by rand()

Question

I have the following:

$products = Mage::getModel(\'catalog/product\')
    ->getCollection()
    ->addAttributeToSort(\'id\', \'RAND()\')
    ->addAt         


        

Answer 1

Using ORDER BY RAND() to return a list of items in a random order will require a full table scan and sort. It can negatively affect performance on large number of rows in the table.

There are several alternative solutions possible of how to optimize this query. Magento provides a native solution for that.

The orderRand() method of Varien_Db_Select and the database adapter allows to specify a random order and leverage index for ORDER BY. Specify a name of some integer indexed column to be used in the ORDER BY clause, for example:

$collection->getSelect()->orderRand('main_table.entity_id');

See Varien_Db_Adapter_Pdo_Mysql::orderRand() for implementation details.