如何防止Firebase中的数据重复？

Question

使用post方法，数据发布如下。每个节点都有一些独特的 ID。那么如何使用firebase中的规则防止重复数据发布到此JSON数据模型？

REST POST URL: https://*****.firebaseio.com/user_details.json

{

"-Ktzg49_ArPtNZ9SDpIw": {
    "email": "amee11315@gmail.com",
    "name": "Abir Hossain Amee",
    "profile_photo": "https:\/\/graph.facebook.com\/1928067980740489\/picture?type=large"
  },
  "-KtzpFMjjcvN7Mooh-4I": {
    "email": "arshohag7@gmail.com",
    "name": "Ashiqur Rahman",
    "profile_photo": "https:\/\/graph.facebook.com\/1570862736318692\/picture?type=large"
  },
  "-KtzpbLGDRBo9dH3uZSZ": {
    "email": "arshohag7@gmail.com",
    "name": "Ashiqur Rahman",
    "profile_photo": "https:\/\/graph.facebook.com\/1570862736318692\/picture?type=large"
  },
  "-Ktzq3HgVp9ykErVXg_8": {
    "email": "arshohag7@gmail.com",
    "name": "Ashiqur Rahman",
    "profile_photo": "https:\/\/graph.facebook.com\/1570862736318692\/picture?type=large"
  }

}

我试过这些规则

{
  "rules": {
    ".read": "true",
    ".write": "true",
        "user_details" : {
            "$email" : {
                ".write": "!data.exists()"
            }
        }      
  }
}

但无法阻止重复或实现规范化。