如何获取Firebase Firestore Android中某个字段的值? [英] How to get value of some field in firebase firestore android?

问题描述

像上一个问题一样，我想获取Firebase Firestore中某个字段的值，而不是使用 DocumentSnapshot

Like upper question, i want to get value of some field in firebase firestore instead of all document with DocumentSnapshot

在SQL SELECT col_1, col_2, col_3 FROM table_name

我该怎么办?

谢谢您的帮助.

推荐答案

Cloud Firestore客户端SDK始终读取并返回完整文档.无法读取文档中字段的子集.

The Cloud Firestore client-side SDKs always read and returns full documents. There is no way to read a subset of the fields in a document.

您可以检索整个文档，然后处理DocumentSnapshot以仅使用您感兴趣的字段.但这意味着您使用的带宽超出了需要.如果您的应用经常出现这种情况，请考虑创建一个辅助集合，其中每个文档仅包含您感兴趣的字段.

You can retrieve the entire document, and then process the DocumentSnapshot to just use the fields you're interested. But this means you're using more bandwidth than needed. If this is a regular occurrence for your app, consider creating a secondary collection where each document contains just the fields you're interested in.

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