Doctrine2渴望加载运行多个查询而不是1 [英] Doctrine2 eager loading runs multiple queries instead of 1

问题描述

我正在使用Symfony2与Doctrine2（最新版本），并且定义了这种关系：

I'm using Symfony2 with Doctrine2 (latest versions) and have this relation defined:

/**
 * @ORM\OneToMany(targetEntity="Field", mappedBy="event", fetch="EAGER")
 * @ORM\OrderBy({"name" = "ASC"})
 */
protected $fields;

该关系的另一面定义为：

The other side of the relation is defined as:

/**
 * @ORM\ManyToOne(targetEntity="Event", inversedBy="fields", fetch="EAGER")
 * @ORM\JoinColumn(nullable=false, onDelete="CASCADE")
 */
protected $event;

当做一个fetchOnyById时，Doctrine运行2个查询。 1获取对象本身，1为相关字段。
我希望这是一个加入，但不是。

When doing a "fetchOnyById", Doctrine runs 2 queries. 1 to fetch the object itself and 1 for the related fields. I would expect this to be a join, but it isn't.

在控制器中完成后，我将对象传递给twig。
在那里我再次检索字段作为对象的属性。
这导致运行另一个查询以再次检索这些字段。

When done in the controller, I pass my object to twig. There I retrieve the fields again as a property of the object. This causes another query to be run to retrieve the fields again.

显然我做错了，就像我会期望只有1个查询运行，3个实际运行。

Clearly I'm doing something wrong, as I would expect only 1 query to be run and 3 are actually run.

推荐答案

我相信这是发生的原因是因为你获取实体，而不是特定的查询。 Doctrine的想法是，您正在获取对象，而不是与数据库进行交互，而是与对象资源进行交互，就像它们与存储实体相关联/引用一样。如果您需要一个像您描述的查询，那么最好使用DQL，但是在这一点上，您不会获取创建的实体，您将获得一个自定义结果。

I believe the reason this is occurring is because you're fetching entities, not a specific query. The idea of Doctrine is that you're fetching objects, not interacting with a database but an object resource as if they're all associated/referenced like stored entities. If you need a query like you're describing you would be better off using DQL but at that point you're not fetching entities created, you're getting a custom result.

我希望这是有道理的。

基本上，您使用的默认关联是获取关联对象而不是连接的查询。

Basically the default association you're using is fetching associated objects not a joined query.

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