Doctrine2 预先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

我将 Symfony2 与 Doctrine2(最新版本)一起使用，并定义了这种关系:

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

/**
 * @ORMOneToMany(targetEntity="Field", mappedBy="event", fetch="EAGER")
 * @ORMOrderBy({"name" = "ASC"})
 */
protected $fields;

关系的另一端定义为:

/**
 * @ORMManyToOne(targetEntity="Event", inversedBy="fields", fetch="EAGER")
 * @ORMJoinColumn(nullable=false, onDelete="CASCADE")
 */
protected $event;

执行fetchOnyById"时，Doctrine 运行 2 个查询.1 获取对象本身，1 获取相关字段.我希望这是一个连接，但它不是.

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.这会导致运行另一个查询以再次检索字段.

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.

显然我做错了什么，因为我希望只运行 1 个查询，而实际运行 3 个.

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

我相信发生这种情况的原因是因为您正在获取实体，而不是特定查询.Doctrine 的想法是您正在获取对象，而不是与数据库交互，而是与对象资源交互，就好像它们都像存储实体一样关联/引用.如果您需要像您所描述的那样的查询，最好使用 DQL，但此时您不会获取创建的实体，而是获得自定义结果.

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，而不是连接查询.

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

这篇关于Doctrine2 预先加载运行多个查询而不是 1的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！