USE INDEX / FORCE INDEX in a Doctrine2 DQL query (with support for multiple tables in the FROM clause).

example.php

<?php

use UseIndexWalker;
use Doctrine\ORM\Query

$query = $em->createQuery("SELECT f FROM Foo f WHERE f.a = 1 and f.b = 2");

$query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, 'UseIndexWalker');
$query->setHint(UseIndexWalker::HINT_USE_INDEX, 'some_index_name');

$query->getResult();

UseIndexWalker.php

<?php

use Doctrine\ORM\Query\SqlWalker;

class UseIndexWalker extends SqlWalker
{
    const HINT_USE_INDEX = 'UseIndexWalker.UseIndex';

    public function walkFromClause($fromClause)
    {
        $sql = parent::walkFromClause($fromClause);
        $index = $this->getQuery()->getHint(self::HINT_USE_INDEX);

        return preg_replace('/( INNER JOIN| LEFT JOIN|$)/', sprintf(' USE INDEX(%s)\1', $index), $sql, 1);
    }
}