不同于注释Symfony 2 / Doctrine 2

Question

What is the difference between these two?

/**
* @ORM\ManyToOne(targetEntity="Category", inversedBy="products",cascade={"remove"})
* @ORM\JoinColumn(name="category_id", referencedColumnName="id") 
*/
protected $category;

and

/**
 *
 * @ORM\ManyToOne(targetEntity="Category", inversedBy="products")
 * @ORM\JoinColumn(name="category_id", referencedColumnName="id", onDelete="CASCADE"))
 */
protected $category;

Thanks !

Answer 1

The first tells the ORM to perform itself the cascade. Hence Doctrine will keep data in memory to perform itself the delete cascade.

The second will tell to the database to perform the onDelete cascade, unloading the process from doctrine.

Remember that the first option will keep in memory the arrays / associations to perform the delete cascade, which can be really heavy.

Typical use case for the first parameter is a case where your data model graph isn't too heavy, and you really want to benfit every entity lifecycle events, even those who are removed using the cascade.

The downside of the second is that you can't benfit these entity lifecycle events, but if your data model / graph is really too heavy, this can be the only option to deal with cascade.