如何使用 Cloud Firestore 中的文档 ID 执行集合组查询 [英] How to perform collection group query using document ID in Cloud Firestore

问题描述

几天前，由于 firestore 显然具有更灵活的查询，我将我的应用程序帖子从实时数据库移到了 cloud firestore.我一直在修改我的代码以使用 firestore 作为新数据库.现在我遇到了一个问题.如何检索Posts"集合中包含特定命名文档的Likes"集合的每个文档?我不知道这是否有意义，所以这是一张展示问题的图片:

So few day ago I moved my apps posts to cloud firestore from realtime database because of the more flexable querying that firestore apparently has. I have been modifying my code to work with firestore as the new database. Now I ran into a problem. How can I retrieve every document within "Posts" collection that has "Likes" collection that contains a specifically named document? I don't know if that makes sense so here's an image showcasing the problem:

我有一个对 firebase 实时数据库的有效查询，但不知道如何使用 firestore 进行查询.是否有可能或我必须更改我的数据库结构?如果我必须改变结构，获得相同结果的最方便的方法是什么?

I had a working query for firebase realtime database but can't figure out how to do it with firestore. Is it possible or do I have to change the structure of my database? If I do have to change the structure, what would be the most convenient way of getting the same result?

推荐答案

这对于集合组查询目前是不可能的.您可能想在 FieldPath.documentId() == 'your-doucment-id' 的查询上放置一个过滤器，但这只是不受支持.FieldPath.documentId() 实际上是一个token，指的是完全唯一的文档id，包括文档的整个路径.

This is currently not possible with collection group queries. You might be tempted to put a filter on the query for FieldPath.documentId() == 'your-doucment-id', but that just isn't supported. FieldPath.documentId() is actually a token that refers to to fully unique document id, which includes the entire path of the document.

解决方法是将文档 ID 作为字段存储在文档中，然后过滤该字段的内容.因此，如果文档有一个名为 id 的字段和文档的 ID，您可以查询 collectionGroup("Likes").whereEquals('id', 'your-document-id').

The workaround is to store the document ID as a field in the document, and filter on the contents of that field instead. So, if the document had a field called id with the ID of the document, you could query for collectionGroup("Likes").whereEquals('id', 'your-document-id').

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