添加和".indexOn":“.value"纳入Firebase规则 [英] Adding and ".indexOn": ".value" into Firebase Rules

问题描述

我正在研究AngularJS和Firebase，并且正在玩一个简单的ChatApp，只是为了了解代码.

I'm studying AngularJS and Firebase and I'm playing with a simple ChatApp, just to understand the code.

我的Firebase数据库结构是这样的:

My Firebase DB structure is like this:

"chat": {
    "messages": {
        "chat1": { [ list of messages ] },
        "chat2": { [ list of messages ] }
    },
    "rooms": {
        "chat1": {
            "users": {
                "user1": true,
                "user2": true
            }
        },
        "chat2": {
            "users": {
                "user2": true,
                "user3": true
            }
        }
    }
}

由于具有Firebase保护规则，我无法在用户节点中添加聊天链接，因此我必须通过在App上使用 orderByChild()查询进行Firebase查询来检索用户的聊天室启动.

Due to Firebase protection Rules I can't add chat link in the user node, than I necessary have to do a Firebase query to retrieve chat rooms for user, using orderByChild() query on App Start Up.

使用Firebase很简单，因为我可以使用以下方式检索所有聊天记录:

Using Firebase is simple than I can retrieve all chat using:

var chatLink = firebase.database().ref('chat/rooms');
chatLink
  .orderByChild('users/' + userId)
  .equalTo(true)
  .once('value', function(chatSnap){

      /* Do Some Stuff Here */

  });

一切正常，但是我在控制台中收到警告:

Every thing work well, but I'm receiving a warning in the console:

FIREBASE警告:使用未指定的索引.考虑在/chat/rooms的安全规则中添加".indexOn":"users/{userId}"以提高性能

FIREBASE WARNING: Using an unspecified index. Consider adding ".indexOn": "users/{userId}" at /chat/rooms to your security rules for better performance

在网络上搜索时，我发现对于变量 orderByChild()查询，我可以在Firebase规则中使用 .indexOn:.value .

Searching on the web, I found that for variable orderByChild() query, I can user .indexOn: .value in my Firebase Rules.

我尝试添加此规则:

{
    "rules": {
        "chat": {
            "rooms": {
                ".indexOn": ".value"
            }
        }
    }
}

但是我仍然总是收到该警告.我该如何解决?

But I'm still receive always that warning. How can i fix it?

非常感谢！

推荐答案

要对该结构建立索引以实现高效查询，您必须为每个用户添加一个索引:

To index this structure to allow efficient querying, you have to add an index for each user:

{
    "rules": {
        "chat": {
            "rooms": {
                ".indexOn": ["users/user1", "users/user2"]
            }
        }
    }
}

这将无法维护，因为您可能会动态添加用户.

That won't be maintainable, since you're likely adding users dynamically.

与NoSQL数据库一样，这意味着您必须扩展/调整数据模型以允许所需的用例.除了为您的用户查询房间外，还要保留每个用户的房间列表(除了您当前的数据之外):

As usual with NoSQL databases, this means you have to expand/adapt your data model to allow the use-case you want. Instead of querying the rooms for their users, keep a list of the rooms for each user (in addition to your current data):

"user_rooms": {
  "user1": {
    "chat1": true
  },
  "user2": {
    "chat1": true,
    "chat2": true
  }
  "user3": {
    "chat2": true
  }

现在，您甚至可以查询用户的聊天室.

Now you can look up the chat rooms for a user without even needing to query.

另请参阅 Firebase查询中有关此分类问题的答案如果child的child包含值.

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