从父节点读取特定叶/子节点的 Firebase 规则

Question

我的 firebase 数据库是这样的

"students" : {
  "firebase_key_1" : {
    "Name" : "blah blah",
    "Address" : "blah blah",
    "Roll No" : "blah blah",
    "Marks" : {
        "Sub1" : "blah",
        "Sub2" : "blah",
        "Sub3" : "blah",
        "Total" : "Total",
    },
    "class" : "blah blah",
    "Transportation" : "blah blah",
    "Department" : "blah blah",
},
  "firebase_key_2" : {
    "Name" : "blah blah",
    "Address" : "blah blah",
    "Roll No" : "blah blah",
    "Marks" : {
        "Sub1" : "blah",
        "Sub2" : "blah",
        "Sub3" : "blah",
        "Total" : "Total",
    },
    "class" : "blah blah",
    "Transportation" : "blah blah",
    "Department" : "blah blah",
},
  "firebase_key_3" : {
    "Name" : "blah blah",
    "Address" : "blah blah",
    "Roll No" : "blah blah",
    "Marks" : {
        "Sub1" : "blah",
        "Sub2" : "blah",
        "Sub3" : "blah",
        "Total" : "Total",
    },
    "class" : "blah blah",
    "Transportation" : "blah blah",
    "Department" : "blah blah",
}
}

我正在使用 rest api 从 firebase 检索数据。休息api url 看起来像 https://domain.firebaseio.com/students.json?orderby="Marks/Total"&startAt=400

我已经通过 firebase 规则为学生总数编制了索引。我得到结果以及额外的数据，例如姓名、class、卷号

我希望输出为

    "firebase_key_1" : {
    "Marks" : {
        "Sub1" : "blah",
        "Sub2" : "blah",
        "Sub3" : "blah",
        "Total" : "Total",
    }
},
"firebase_key_2" : {
    "Marks" : {
        "Sub1" : "blah",
        "Sub2" : "blah",
        "Sub3" : "blah",
        "Total" : "Total",
    }
},
"firebase_key_3" : {
    "Marks" : {
        "Sub1" : "blah",
        "Sub2" : "blah",
        "Sub3" : "blah",
        "Total" : "Total",
    }
}

是否可以通过 RestAPI 或 Rules 执行此操作。

是否有任何规则可以定义要读取的节点，例如

{
 "users":{
   "students":{
      ".read" : ["$firebaseKey/Marks"],
      ".write" : true,
   }
   }

这样我就可以使用 Rest api 从父节点检索所需的值。

如果有任何其他建议，那就太好了。

提前致谢

Answer 1

Firebase 数据库始终 returns 完整节点。不可能获得与您的查询匹配的每个节点的子集。要么返回整个节点，要么不返回。

通常这种类型的请求表明您合并了多种类型的数据，您应该将它们分开。在您的情况下，看起来您应该有两个顶级集合：students 和 studentMarks。在 students 下，您保留每个学生的属性，以他们的学生 ID 为关键字。在 studentMarks 下，您保留每个学生的分数，同样由他们的学生 ID 键入。

所以：

"students" : {
  "firebase_key_1" : {
    "Name" : "blah blah",
    "Address" : "blah blah",
    "Roll No" : "blah blah",
    "class" : "blah blah",
    "Transportation" : "blah blah",
    "Department" : "blah blah",
  },
  "firebase_key_2" : {
    "Name" : "blah blah",
    "Address" : "blah blah",
    "Roll No" : "blah blah",
    "class" : "blah blah",
    "Transportation" : "blah blah",
    "Department" : "blah blah",
  },
  "firebase_key_3" : {
    "Name" : "blah blah",
    "Address" : "blah blah",
    "Roll No" : "blah blah",
    "class" : "blah blah",
    "Transportation" : "blah blah",
    "Department" : "blah blah",
  }
},
"studentMarks": 
  "firebase_key_1" : {
    "Sub1" : "blah",
    "Sub2" : "blah",
    "Sub3" : "blah",
    "Total" : "Total",
  },
  "firebase_key_2" : {
    "Sub1" : "blah",
    "Sub2" : "blah",
    "Sub3" : "blah",
    "Total" : "Total",
  },
  "firebase_key_3" : {
    "Sub1" : "blah",
    "Sub2" : "blah",
    "Sub3" : "blah",
    "Total" : "Total",
  }
}

由于您在 students 和 studentMarks 之间使用相同的密钥，您可以轻松地为用户准备两组数据。但现在您也可以只读取每个用户的属性，或者只读取一组用户的标记。

从父节点读取特定叶/子节点的 Firebase 规则

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