如何从Firestore中的多个文档中的数组中删除元素?

问题描述

我有一组用户.每个用户都有一个名为 favoriteNames 的数组.

I have a collection of users. Each user has an array named favoriteNames.

root <- [Firestore]
 users <- [Collection]
   uid <- [Document]
    favoriteNames: ["Ana", "Jane", "Dave"] <- [Array]
   uid<- [Document]
    favoriteNames: ["Ana", "Merry", "John"] <- [Array]

我要删除"Ana"从所有文件.这是我尝试过的:

I want to remove "Ana" from all documents. This is what I tried:

usersRef.whereArrayContains("favoriteNames", FieldValue.arrayRemove("Ana").get()

但是它不起作用.如何删除"Ana"来自所有阵列?

But it doesn't work. How can I remove "Ana" from all arrays?

推荐答案

无法执行类似SQL的"update where"使用Firestore输入查询.如果要更新多个文档，则必须分别更新每个文档.如果需要，您可以使用事务或批处理写入来自动进行所有更新.

It's not possible to do a SQL-like "update where" type query with Firestore. If you have multiple documents to update, you will have to update each one individually. You can use a transaction or batch write to do all the updates atomically, if needed.

至少，您要做的是:

1. 查询所有要更新的文档.这将涉及对所有"数组包含查询进行; Ana".

1. Query for all the documents to update. This will involve doing an array-contains query for all "Ana".

usersRef.whereArrayContains("favoriteNames", "Ana")

迭代查询结果.

Iterate the query results.

对于每个匹配的 DocumentSnapshot ，获取其DocumentReference并将 update()与 FieldValue.arrayRemove("Ana")

For each matching DocumentSnapshot, get its DocumentReference and use update() with FieldValue.arrayRemove("Ana")

snapshot.reference.update("favoriteNames", FieldValue.arrayRemove("Ana"))

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