无法查询多个值的Firestore数据库 [英] Cannot query Firestore database on multiple values

问题描述

我有一个充满汽车的数据库. JSON 格式是这样的:

I have a database full with cars. The JSON format is this:

docId: {
        "countries": ["Netherlands"]
        "cities": ["Amsterdam"]
   }

我无法查询两个数组.

db.collection("EU-CARS")
    .whereArrayContains("countries", "Netherlands")
    .whereArrayContains("cities", "Amsterdam");

如何解决这个问题?

推荐答案

正如您已经注意到的，Firestore允许您仅使用一个 whereArrayContains()方法调用来过滤汽车.如果您将使用多个，则将发生如下错误:

As you already noticed, Firestore allow you to filter your cars using only one whereArrayContains() method call. If you will use more than one, an error like this will occur:

原因:java.lang.IllegalArgumentException:无效的查询.查询仅支持具有单个包含数组的过滤器.

Caused by: java.lang.IllegalArgumentException: Invalid Query. Queries only support having a single array-contains filter.

有两种方法可以解决此问题.第一个方法是像这样更改您的汽车文档的结构:

There are two ways in which you can solve this. The first one would be to change the structure your car document like this:

docId
  |
  --- filters
       |
       --- "country": "Netherlands"
       |
       --- "city": "Amsterdam"

通过这种方式，您可以使用以下方法过滤数据库:

In this way you can filter your database using:

Query query = db.collection("EU-CARS").
    .whereEqualTo("filters.country", "Netherlands")
    .whereEqualTo("filters.city", "Amsterdam");

在Firestore中允许束缚多个 whereEqualTo()方法.

Chaining multiple whereEqualTo() methods is permitted in Firestore.

或者，如果您仍然想使用数组，只需将两个名称连接成一个单数:

Or if you still want to use arrays, simply concatenate both names into a sigle one:

docId
  |
  --- "countries_cities": ["Netherlands_Amsterdam", "Netherlands_Utrecht"]

相应的查询应如下所示:

The corresponding query should look like this:

db.collection("EU-CARS")
    .whereArrayContains("countries_cities", "Netherlands_Amsterdam");

如果您有多个国家/地区，则文档的结构应如下所示:

If you have multiple countries/cities, then the structure of your document should look like this:

docId
  |
  --- filters
       |
       --- "Netherlands": true
       |
       --- "Amsterdam": true
       |
       --- "Utrecht": true

通过这种方式，您可以使用以下方法过滤数据库:

In this way you can filter your database using:

Query query = db.collection("EU-CARS").
    .whereEqualTo("filters.Netherlands", true)
    .whereEqualTo("filters.Amsterdam", true);

这篇关于无法查询多个值的Firestore数据库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！