Firestore安全规则，以检查角色用户名是否已存在 [英] Firestore security rule to check if character username already exists

问题描述

我在数据库(firestore)中具有以下字符收集结构

I have following character collection structure in my database (firestore)

/characters/{uid}
 - username: string
 - clan: string
 - mana: number
 - health: number
 etc...

我正在尝试使用以下逻辑找出/characters/{uid}的安全规则

I am trying to figure out a security rule for /characters/{uid} with following logic

service cloud.firestore {
  match /databases/{database}/documents {

    // Characters
    match /characters/{characterID} {
      allow create: if isValidUsername();
    }
  }
}

此处函数isValidUsername检查各种内容，例如长度，特殊字符等...但是我不知道的一件事是如何检查函数内部的后续内容

here function isValidUsername checks for various things like length, special characters etc... but one thing I can't figure out is how to check following inside of the function

确保request.resource.data.username是唯一的，即在/characters集合的任何其他文档中都没有.

Make sure that request.resource.data.username is unique i.e. not present inside any other document of /characters collection.

推荐答案

TL; DR:只有通过创建额外的集合才能实施唯一性.

TL;DR: Enforcing uniqueness is only possible by creating an extra collection.

在当前结构中，要知道用户名是否唯一，您需要阅读每个文档.这是非常低效的，而且最重要的是，在安全规则中是不可能的，因为每个规则只能读取几个文档.

In your current structure, to know if a username is unique, you will need to read each document. This is incredibly inefficient, and on top of that it isn't possible in security rules, since they can only read a few documents per rule.

诀窍是创建一个额外的集合usernames，在该集合中您还为每个用户提供了一个文档，但是现在每个文档的键/ID是用户名.通过这样的集合，您可以检查某个文档的存在，这是安全规则中的原始操作.

The trick is to create an extra collection usernames, where you also have a document for each user, but now the key/ID of each document is the username. With such a collection, you can check for the existence of a certain document, which is a primitive operation in the security rules.

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