Doctrine2一对一关系自动加载查询 [英] Doctrine2 one-to-one relation auto loads on query

问题描述

我的查询如下所示：

我的用户实体有一对一的关系，如下所示：

My user entity has a one-to-one relation that looks like this:

/**
 * @var UserProfile
 *
 * @ORM\OneToOne(targetEntity="UserProfile",mappedBy="user")
 */
private $userProfile;

每当我查询选择多个用户对象时，它会为每个用户创建一个附加的select语句来查询对于UserProfile数据，即使我没有通过get方法访问它。我并不总是需要UserProfile数据，我当然不希望每次显示一个用户列表时加载这些数据。

Anytime I make a query to select multiple user objects, it creates an additional select statement per user to query for the UserProfile data even though I am not accessing it through a get method. I don't always need the UserProfile data, and I certainly don't want to load this data every single time I'm displaying a list of users.

任何想法为什么这些查询在运行时执行？

Any idea why these queries are executed at run time?

推荐答案

这里是解决方案解释细节：

Here is solutions explain with details :

https://groups.google.com/forum/#!topic/ doctrine-user / fkIaKxifDqc

映射中的fetch是一个提示，即如果可能的话
原则做到这一点，但如果不可能的话，显然没有。
延迟加载的代理在技术上并不总是可能的。
不可能的情况是：

"fetch" in the mapping is a hint, that is, if it is possible Doctrine does that, but if its not possible, obviously it does not. Proxying for lazy-loading is simply not always possible, technically. The situations where its not possible are:

1）从反向到所有方一对一（仅出现在
双向one-一对一关联）。前提条件a）以上不能
得到满足。 2）与层次结构的一对一/多对一关联，并且
目标类具有子类（不是类层次结构中的叶）。
前提条件b）无法满足

1) one-to-one from inverse to owning side (appears only in bidirectional one-to-one associations). Precondition a) above can not be met. 2) one-to-one/many-to-one association to a hierarchy and the targeted class has subclasses (is not a leaf in the class hierarchy). Precondition b) above can not be met.

在这些情况下，代理在技术上是不可能的。

In these cases, proxying is technically not possible.

您可以选择避免此n + 1问题：

Your options to avoid this n+1 problem:

1）通过DQL获取加入：select c，ca from Customer join c.cart ca。
单个查询但是加入，但是，加入一对一关联是
相对便宜。

1) fetch-join via DQL: "select c,ca from Customer join c.cart ca". Single query but join, however, joins on to-one associations are relatively cheap.

2）强制部分对象。没有其他查询，但
也没有lazy-load：$ query-> setHint（Query :: HINT_FORCE_PARTIAL_LOAD，
true）

2) force partial objects. No additional queries but also no lazy-load: $query->setHint(Query::HINT_FORCE_PARTIAL_LOAD, true)

3）如果替代结果格式（即getArrayResult（））是
足够用于一个用例，这些也避免了这个问题。

3) if an alternative result format (i.e. getArrayResult()) is sufficient for a use-case, these also avoid this problem.

本杰明有一些关于自动批处理的想法这些加载到
避免n + 1个查询，但这并不改变代理是
并不总是可能的事实。

Benjamin had some ideas about automatic batching of these loads to avoid n+1 queries but this does not change the fact that proxying is not always possible.

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