在地图包含字符串的Firestore查询 [英] Firestore query where map contains string

问题描述

数据结构:

houses (collection)
  name (string)
  users (map)
    90c234jc23 (map)
      percentage: 100% (string/number)

规则:

allow read: request.auth.uid in resource.data.users;

问题是当我尝试查询用户拥有的房屋时:

The problem is when I try to query houses which user owns:

FirebaseFirestore.getInstance().collection(House.COLLECTION)
//                .whereArrayContains(House.USERS_FIELD, currentUser.getUid()) // does not work
                .whereEqualTo("users." + currentUser.getUid(), currentUser.getUid()) // does not work either
                .get()

没有结果返回.

推荐答案

由于不存在"map-contains-key"运算符，因此无法在firestore中执行此类查询.但是，有一种非常简单的解决方法，可以通过对数据结构进行细微调整来实现.

You cannot perform this type of query in firestore as there is no 'map-contains-key' operator. However, there are very simple workarounds for implementing this by making slight adjustments to your datastructure.

要求:要使该解决方案有效，每个地图值必须在Firestore查询中唯一标识，这意味着它不能是地图或数组.

Requirement: For this solution to work, each map value has to be uniquely identifyable in a firestore query, meaning it cannot be a map or an array.

如果您的案件符合列出的要求，则可以使用 @Dennis Alund的解决方案，其中建议使用以下数据结构:

If your case meets the listed requirements, you can go with @Dennis Alund's solution which suggests the following data structure:

{
  name: "The Residence",
  users: {
    uid1: 80,
    uid2: 20
  }
}

常规解决方案

如果地图值是地图或数组，则需要为每个值添加一个属性，该属性在此类型的所有已创建值中将保持不变.这是一个示例:

General Solution

If your map values are maps or arrays, you need to add a property to each value which will be constant across all created values of this type. Here is an example:

{
  name: "The Residence",
  users: {
    uid1: {
      exists: true,
      percentage: 80,
      ...
    },
    uid2:  {
      exists: true,
      percentage: 20,
      ...
    },
  }
}

现在您可以简单地使用查询:

Now you can simply use the query:

_firestore.collection('houses').whereEqualTo('users.<uid>.exists', true)

这篇关于在地图包含字符串的Firestore查询的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！