Google App Engine的“webapp”中是否有“ForeignKey”？ [英] Is there something like `ForeignKey` in Google App Engine's `webapp`?

问题描述

我正在使用Google App Engine和 webapp 框架。在 webapp 中有没有像Django的 ForeigKey ？即我有一个模型，我希望它有一个属性/字段指向另一个模型。可能吗？

解决方案

db.ReferenceProperty 。在使用它时需要注意两点：自动解引用（这是另一个数据存储RPC调用），被引用的实体不需要存在（所以你需要手动检查它）。

当使用db.ReferenceProperty时，确保使用Appstats来避免串行读取实体。 Nick Johnson有一篇文章，获取引用的实体。

I'm using Google App Engine with their webapp framework. Is there something like Django's ForeigKey in webapp? i.e. I have a model and I want it to have a property/field that points at another model. Possible?

解决方案

There is a db.ReferenceProperty. You need to be aware of two things when using it: automatic dereferencing (which is another datastore RPC call) and the entity being referenced is not required to exist (so you will need to manually check it).

When using db.ReferenceProperty make sure you use Appstats to avoid fetching entities in serial. Nick Johnson has an article that explains how to pre-fetch referenced entities.

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