在 Cloud Firestore 中查找具有特定参考的所有文档 [英] Finding all docs with specific reference in Cloud Firestore

问题描述

在 Cloud Firestore 上，我的文档以这种方式引用了另一个文档:

在我的示例中，文档 Collection A/WJQ9yx67RrqHWQoEp0e2 指的是文档 Collection B/rFOEwdw5go4dbitOCXyC，但当然，可以无限引用提到的文档.

现在我想找出 Collection A 的所有文档，这些文档涉及这个非常具体的文档 Collection B/rFOEwdw5go4dbitOCXyC.

这怎么可能?我如何才能做到这一点?

Firebase 的文档对此有点不清楚.

解决方案

你说得对，很遗憾，文档中没有实际使用 Reference 数据类型的例子，事实上唯一的支持的数据类型部分中提到了它.

最终，Reference 可以像 Firestore 中可用的任何其他数据类型一样使用，因此可用于过滤 &也对数据进行排序.

要实现您的目标，您需要构造一个 Reference 指向 Collection B 中的文档，然后使用 where 子句根据 Collection A 的 reference 值过滤数据.例如在 JavaScript 中:

//创建对要搜索的特定文档的引用var reference = db.collection("Collection B").doc("rFOEwdw5go4dbitOCXyC");//构造一个查询来过滤与引用匹配的文档var query = db.collection("Collection A").where("reference", "==", reference);

查看 isEqual() 在 Firebase JavaScript SDK 中的源代码，Reference(扩展 Query)的比较是通过简单的检查来执行的路径匹配:

<块引用>

 isEqual(other: Query): boolean {//[...]const sameRepo = this.repo === other.repo;const samePath = this.path.equals(other.path);const sameQueryIdentifier =this.queryIdentifier() === other.queryIdentifier();返回 sameRepo &&相同路径 &&相同的查询标识符；}

这看起来很像在两者上调用 toString() 并比较字符串值.

我昨天制作了一个类似示例，这让我测试了存储参考资料的可能用途代码>，所以这也适用于这里.

On Cloud Firestore I have documents with reference to another document this way:

In my example, document Collection A/WJQ9yx67RrqHWQoEp0e2 is referring to document Collection B/rFOEwdw5go4dbitOCXyC, but there of course, could be infinitely docs referring to one mentioned.

Now I would like to find out all the docs of Collection A which are referring to this very specific document Collection B/rFOEwdw5go4dbitOCXyC.

How is this possible? How I can achieve this?

Documentation of Firebase is bit unclear with this.

解决方案

You're right, there's unfortunately no example of actually making use of a Reference data type in the documentation, in fact the only a mention of it is in the Supported Data Types section.

Ultimately though, a Reference can be used just like any other data type available in Firestore, so can be used to filter & sort data too.

To achieve what you're after, you would need to construct a Reference that points to the document in Collection B and then use a where clause to filter data on the reference value of Collection A. For example in JavaScript:

// Create a reference to the specific document you want to search with
var reference = db.collection("Collection B").doc("rFOEwdw5go4dbitOCXyC");

// Construct a query that filters documents matching the reference
var query = db.collection("Collection A").where("reference", "==", reference);

Looking at the source for isEqual() in the Firebase JavaScript SDK, comparing of a Reference (extends Query) is performed by simply checking that the paths match:

  isEqual(other: Query): boolean {
    // [...]
    const sameRepo = this.repo === other.repo;
    const samePath = this.path.equals(other.path);
    const sameQueryIdentifier =
      this.queryIdentifier() === other.queryIdentifier();

    return sameRepo && samePath && sameQueryIdentifier;
  }

This would seem to be much like calling toString() on both and comparing the string values.

I produced a similar example yesterday which lead me to test the possible uses of storing a Reference, so that may also apply here.

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