doctrine-orm - 为什么 Doctrine 坚持持久化引用的托管实体？

Question

根据 Doctrine 2.0 文档 ( http://docs.doctrine-project.org/en/2.0.x/reference/working-with-objects.html ) a

..preexisting managed entity, is ignored by the persist operation. However, the persist operation is cascaded to entities referenced by X, if the relationships from X to these other entities are mapped with cascade=PERSIST or cascade=ALL (see “Transitive Persistence”)."

我的理解是，级联到引用的托管实体应该导致引用的实体被持久化操作忽略(案例 3):

Persistence by Reachability: Cascade Persist

1. New entities in a collection marked as cascade persist will be directly persisted by Doctrine.
2. New entities in a collection not marked as cascade persist will produce an Exception and rollback the flush() operation.
3. Collections without new entities are skipped.

然而，事实并非如此。我有一个托管 Channel 实体，其中包含 1:n 个 Properties 和 Data 实体。创建 Channel 实体时，会检索但不会修改一些属性。

当我添加数据并通过以下方式持久化实体时

$channel->addData(new Model\Data($channel, $timestamp, $value));
$em->persist();

我可以看到用于编写新的 Data 实体的 SQL，但也可以看到对现有 Properties 的更新(具有未更改的旧值)。

为什么 Doctrine (2.4.1) 会保留被管理实体的关系？

实体定义如下所示:

class Channel extends Entity {
    /**
     * @OneToMany(targetEntity="Data", mappedBy="channel", cascade={"persist"}, orphanRemoval=true)
     * @OrderBy({"timestamp" = "ASC"})
     */
    protected $data = NULL;

    /**
     * Constructor
     */
    public function __construct($type) {
        parent::__construct($type);
        $this->data = new ArrayCollection();
    }

    /**
     * Add a new data to the database
     */
    public function addData(\Volkszaehler\Model\Data $data) {
        $this->data->add($data);
    }

    ...
}

abstract class Entity {

    /**
     * @OneToMany(targetEntity="Property", mappedBy="entity", cascade={"remove", "persist"}, orphanRemoval=true)
     * @OrderBy({"key" = "ASC"})
     */
    protected $properties = NULL;

    /**
     * Constructor
     *
     * @param string $type
     */
    public function __construct($type) {
        if (!Definition\EntityDefinition::exists($type)) {
            throw new \Exception('Unknown entity type: \'' . $type . '\'');
        }

        $this->properties = new Collections\ArrayCollection();
    }

    ...
}

Answer 1

我终于发现 Doctrine 不坚持持久化引用的托管实体。

在上述情况下，我已经修改了相关实体(更改了某些属性的类型)，由于在计算更改集时它的 === 比较，Doctrine 确实解释为更新。

有一些关于使用 PostFlush 事件来防止这种情况的讨论，但目前还没有定论:https://github.com/doctrine/doctrine2/pull/382#issuecomment-43421295