Firestore:ID在集合中或全局是唯一的吗? [英] Firestore: Are ids unique in the collection or globally?

问题描述

对于我的数据库结构，我需要知道Firebase Cloud Firestore中自动生成的标识符在集合中还是在整个数据库中是唯一的.

For the structure of my database I need to know if the automatically generated identifiers in Firebase Cloud Firestore are unique in the collection or in the whole database.

该怎么做?

推荐答案

通过调用 add() 并不与您调用add()的集合相关.取而代之的是，它们是随机标识符，从统计学上保证是唯一的.对于Firestore(和Firebase实时数据库)，这些密钥是在客户端生成的.

The keys generated by calling add() in Firestore are not tied to the collection on which you call add(). Instead they are random identifiers that are statistically guaranteed to be unique. In the case of Firestore (and Firebase Realtime Database) these keys are generated client-side.

如果您有兴趣，请查看Firestore JavaScript SDK如何实现该逻辑:

If you're interested, have a look at how the Firestore JavaScript SDK implements the logic:

1. add调用doc()

doc调用AutoId.newId()

AutoId.newId()生成客户端ID

AutoId.newId() generates a client-side ID

其本身的逻辑类似于Firebase Realtime数据库如何生成其推送ID.主要区别似乎在于Firestore的自动生成的密钥不是基于本地时间戳，因此无法有效地使用它们来对集合中的文档进行排序.

In itself the logic is similar to how the Firebase Realtime Database generates its push IDs. The main difference seems to be that Firestore's auto-generated keys are not based on the local timestamp, so they cannot be meaningfully used to order the documents in the collection.

这篇关于Firestore:ID在集合中或全局是唯一的吗?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！