Symfony doctrine DQL random result in Query with MaxResult - php

Question

How can I get a random result with an dql Query?
This is my query:
$firstCategoryId = 50;
$repository = $this->entityManager->getRepository(BaseProduct::class);
$products = $repository->createQueryBuilder('p')
->join('p.categories', 'c')
->where('c.id = :categoryId')
->setParameter('categoryId', $firstCategoryId)
->getQuery()
->setMaxResults(4)
->getResult();
This returns me always the first 4 products.
Lets say the category with ID 50 has over 100 products. And what I want is querying randomly 4 articles from category with ID 50. But how? Is this possible? Of course I can set no Max Result and than do it with PHP... but this is not a good solution because of performance.

Answer 1

You need to create dql function for that. https://gist.github.com/Ocramius/919465 you can check that.
namespace Acme\Bundle\DQL;
use Doctrine\ORM\Query\Lexer;
use Doctrine\ORM\Query\Parser;
use Doctrine\ORM\Query\SqlWalker;
use Doctrine\ORM\Query\AST\Functions\FunctionNode;
class RandFunction extends FunctionNode
{
public function parse(Parser $parser)
{
$parser->match(Lexer::T_IDENTIFIER);
$parser->match(Lexer::T_OPEN_PARENTHESIS);
$parser->match(Lexer::T_CLOSE_PARENTHESIS);
}
public function getSql(SqlWalker $sqlWalker)
{
return 'RAND()';
}
}
After that open your config.yml file and add autoload that RandFunction.
orm:
dql:
numeric_functions:
Rand: Acme\Bundle\DQL\RandFunction
And your query must be like:
$firstCategoryId = 50;
$repository = $this->entityManager->getRepository(BaseProduct::class);
$products = $repository->createQueryBuilder('p')
->join('p.categories', 'c')
->addSelect('RAND() as HIDDEN rand')
->where('c.id = :categoryId')
->orderBy('rand')
->setParameter('categoryId', $firstCategoryId)
->getQuery()
->setMaxResults(4)
->getResult();