I have the following database scheme:
table \'products\'
id
category_id
and of course a category table, just with an id.
The data look
Use this helper function:
<?php
use Doctrine\ORM\EntityManager;
/**
* Retrieve one random item of given class from ORM repository.
*
* @param EntityManager $em The Entity Manager instance to use
* @param string $class The class name to retrieve items from
* @return object
*/
function getRandomDoctrineItem(EntityManager $em, $class)
{
static $counters = [];
if (!isset($counters[$class])) {
$this->counters[$class] = (int) $this->manager->createQuery(
'SELECT COUNT(c) FROM '. $class .' c'
)->getSingleScalarResult();
}
return $em
->createQuery('SELECT c FROM ' . $class .' c ORDER BY c.id ASC')
->setMaxResults(1)
->setFirstResult(mt_rand(0, $counters[$class] - 1))
->getSingleResult()
;
}
Example usage:
$randomItem = getRandomDoctrineItem($em, 'Application\Entity\Post');
You first have to count the total number of products, then generate a random offset to select a random product.
This should get you started:
$count = $this->createQueryBuilder('u')
->select('COUNT(u)')
->getQuery()
->getSingleScalarResult();
And then you can generate a random number between your 1 and the total number of rows.
return $this->createQueryBuilder('u')
->where('u.category = :category')
->setFirstResult(rand(0, $count - 1))
->setMaxResults(1)
->setParameter('category', $category->getId())
->getQuery()
->getSingleResult()
;
Which translates to:
SELECT * FROM products WHERE category_id = ? LIMIT 1, {random offset}