防止主义获取相关实体

Question

I have a User entity which has One-To-Many association with Account entity:

/**
 * @var Account[]
 *
 * @ORM\OneToMany(
 *     targetEntity="AppBundle\Account",
 *     mappedBy="user",
 *     cascade={"persist", "remove"},
 *     orphanRemoval=true
 * )
 */
protected $accounts;

I'm fetching a list of users and joining accounts to them:

$builder = $this->getEntityManager()->createQueryBuilder()
    ->select('U')
    ->from('Model:User', 'U')
    ->leftJoin('U.accounts', 'A')
;

However, when I'm trying to access fetched accounts of the user I can see that Doctrine are making additional queries to the database to fetch accounts for each user.

foreach ($users as $user) {
    foreach ($user->getAccounts() as $account) {
        // This triggers additional Doctrine query.
        var_dump($account->getId());
    }
}

I'm running this code as a batch job and I want to achieve maximum performance by pre-loading users with accounts and not to issue additional queries later.

Why Doctrine makes additional queries and how to prevent this?

I've tried to use fetch="EXTRA_LAZY" option for OneToMany association, but without any luck, the results are the same.

Answer 1

You must add the account data to the select statement:

$builder = $this->getEntityManager()->createQueryBuilder()
    ->select('U')
    ->from('Model:User', 'U')
    ->addSelect('A')
    ->leftJoin('U.accounts', 'A')
;

Regarding the fetch, fetch="EXTRA_LAZY" is for loading less data. You probably want fetch="EAGER" which will automatically load related entities.