Firestore删除文档及其引用的所有文档 [英] Firestore delete document and all documents referencing it

问题描述

这个问题与Firebase（+ Flutter）有关

this question is regarding Firebase (+ Flutter)

是否可以删除文档以及引用该文档的所有文档？

is it possible to delete a document and all documents referencing it?

假设我具有这样的结构：

Lets assume i have a structure like this:

-users (collection)
  - name
  - bookmarks ((sub)collection)
    - postId
-post (collection)
  - userId
  - name
  - ...

现在，如果我删除帖子，我想删除所有引用该帖子的书签。 （来自所有用户）。有自动的方法吗（来自RDBMS）。

Now if i delete a post, i want to delete all bookmarks referencing that post. (From all users). Is there an automatic way (coming from RDBMS).

另一个问题：
如何查询所有帖子并加入用户信息。

Another question: How can i query all posts and "join" the user infos.

类似这样的东西：

return firestore
        .collection("posts")
        .orderBy("createdAt")
        .snapshots(); // I want to join the userInformation

这些嵌套查询是否等于api限制？

And are these nested queries then and counting to the api limit?

预先感谢

推荐答案

您必须查询文档并然后批量删除它们。我不使用子集合，也不打算查询这些子集合，但是使用根级别架构，您可以删除带有标准Firestore删除的帖子，并引用documentID。假设documentID与您的 postID字段相同（如果不是，则重构您的架构），然后：

you have to query the docs and then batch delete them. i don't use subcollections, and i'm not going to look up how to query them, but with a root level schema you'd delete the post with a standard firestore delete, referencing the documentID. assuming the documentID is the same as your 'postID' field (and if it isn't, refactor your schema) you'd then:

final WriteBatch _batch = Firestore.instance.batch();

  QuerySnapshot _query = await dbUsers.where('postId', isEqualTo: thatDocumentID).getDocuments();

  _query.documents.forEach((doc) {
    _batch.delete(dbUsers.document(doc.documentID));
  });

  await _batch.commit();

请注意，一次只能进行500次批处理：

be aware that batches can only be done 500 at a time:

https://firebase.google.com/docs / firestore / manage-data / transactions

所以您必须拆分 _batch.commit（）必要时调用。

so you'd have to split up your _batch.commit() calls as necessary.

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