删除自引用@ManyToMany连接

Question

我有一个自引用实体Product

<?php
/** @Entity @Table(name="products") **/
class Product
{
    /** @Id @Column(type="integer") @GeneratedValue **/
    protected $id;
    /** @Column(type="string", nullable=true) **/
    protected $name;

    /**
     * @ManyToMany(targetEntity="Product", mappedBy="connectedBy", cascade={"all"})
     */
    protected $connectedWith;

    /**
     * @ManyToMany(targetEntity="Product", inversedBy="connectedWith", cascade={"all"})
     * @JoinTable(name="connection",
     *      joinColumns={@JoinColumn(name="product_id", referencedColumnName="id")},
     *      inverseJoinColumns={@JoinColumn(name="connected_product_id", referencedColumnName="id")}
     *      )
     */
    protected $connectedBy;

    public function __construct()
    {
        $this->connectedWith = new \Doctrine\Common\Collections\ArrayCollection();
        $this->connectedBy = new \Doctrine\Common\Collections\ArrayCollection();
    }
    public function getConnected()
    {
        return $this->connectedWith;
    }

    public function addConnection(Product $product)
    {
        $this->connectedWith->add($product);
        $product->connectedBy->add($this);
    }

    public function removeConnection(Product $product)
    {
        $this->connectedBy->removeElement($product);
        $this->connectedWith->removeElement($product);
    }
}

接下来，我创建了两个产品(I 1和2)和两个产品之间的连接：

mysql> select * from products;
+----+------+
| id | name |
+----+------+
|  1 | NULL |
|  2 | NULL |
+----+------+
2 rows in set (0.00 sec)

mysql> select * from connection;
+------------+----------------------+
| product_id | connected_product_id |
+------------+----------------------+
|          2 |                    1 |
+------------+----------------------+
1 row in set (0.01 sec)

现在，我要删除与以下代码的连接：

$product1 = $entityManager->find('Product', 1);
$product2 = $entityManager->find('Product', 2);
$product1->removeConnection($product2);
$entityManager->persist($product1);
$entityManager->flush();

$product3 = $entityManager->find('Product', 1);
print count($product3->getConnected()) . "\n";

正如预期的那样，代码打印0作为其结果。但是当我查看数据库时，连接条目仍然存在。原因是什么呢?怎么解决的？

我已经试过$entityManager->persist($product2)了，但没有结果。

Answer 1

我做了更多的研究，自己找到了解决方案：

我的函数removeConnection()有一个错误:我从connectedBy和connectedWith这两个列表中删除了产品，这是错误的。相反，我应该像在addConnection()中那样做

$this->connectedWith->removeElement($product);
$product->connectedBy->removeElement($this);