什么是firestore引用数据类型适合？ [英] What is firestore Reference data type good for?

问题描述

我只是在探索新的Firebase Firestore，它包含一个名为 参考 。我不清楚这是什么。

• 是否像外键？


• 
  
• 如果引用是否可以用来指向位于其他位置的集合？ c>是一个实际的参考，我可以用它来查询？例如，我可以有一个直接指向用户的引用，而不是将userId存储在文本字段中？我可以使用这个用户参考进行查询吗？
  
  

  解决方案

  引用非常像外键。
  
  

  当前发行的SDK不能存储对其他项目的引用。在一个项目中，引用可以指向任何其他集合中的任何其他文档。
  
  

  您可以像查询其他任何值一样在查询中使用引用：用于过滤，排序和分页startAt / startAfter）。
  
  

  与SQL数据库中的外键不同，引用对于在单个查询中执行连接是无用的。您可以使用它们进行依赖性查找（看起来像加入），但要小心，因为每一跳都会导致服务器再次往返。

  
  

  I'm just exploring the new Firebase Firestore and it contains a data type called reference. It is not clear to me what this does.

  • Is it like foreign key?
  • Can it be used to point to a collection that is located somewhere else?
  • If reference is an actual reference, can I use it for queries? For example can I have a reference that points directly to the user, instead of storing the userId in a text field? And can I use this user reference for querying?

  解决方案

  References are very much like foreign keys.

  The currently released SDKs cannot store references to other projects. Within a project references can point to any other document in any other collection.

  You can use references in queries like any other value: for filtering, ordering, and for paging (startAt/startAfter).

  Unlike foreign keys in a SQL database, references are not useful for performing joins in a single query. You can use them for dependent lookups (which seem join like), but be careful because each hop will result in another round trip to the server.

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