使用onSnapshot的索引对字段不等于值的Firestore查询 [英] Firestore query where field is not equal to value using indexes with onSnapshot

问题描述

我正在尝试获取当前用户正在对话的所有看不见的消息.问题是我不知道如何排除其他用户看到的消息，而仅获取当前用户看到的消息，因此我可以执行allMessages - allReadMessages = unread messages count

I am trying to get all unseen messages that the current user has in conversation. The problem is that I do not know how to exclude other user seen messages and get only current user seen messages so I can do allMessages - allReadMessages = unread messages count

这是我的功能，试图实现我所解释的内容:

//helper to get unread messages count
  async getUnseenMessagesCount(chatAuthor) {
    const collectionRef = (await firestore()).collection(this.collectionPath)
    try {
      collectionRef
    .get()
    .then(() => {
      collectionRef
        .where('seenBy', '==', '')
        .orderBy('author')
        .where('author', '>', store.getters['authentication/user'].id)
        .onSnapshot(snapshot => {
          snapshot.docChanges().forEach(snap => {
            console.log(snapshot.docs.length)
            if (snap.type === 'added') {
              store.commit(
                'chats/setUnreadMessagesCount',
                snapshot.docs.length
              )
              f.push(snapshot.docs.length)
            }
          })
        })
    })
    .catch(error => {
      console.log(error)
    })       } catch (error) {
      console.log(error)
    }
  }

这些是firebase内部的索引(在我的情况下甚至需要它们吗?):

如何实现我的解释?任何帮助深表感谢！

How can I achieve what I explained? Any help is much appreciated!

推荐答案

当我第一次使用Firestore时，这些事情对我来说也是一个问题.很难执行简单的计数查询.

When I user firestore for the first time, these things was also a problem for me. Being very hard to do a simple count query.

因此，对于您的问题，简单的答案是您可以获取经过身份验证的用户ID，并在其中添加另一个查询之类的内容

So for your question, the simple answer is you can get the authenticated user id and add another where query something like

firebase.auth().onAuthStateChanged((user) => {
  if (user) {
    // User logged in already or has just logged in.
    console.log(user.uid);
  } else {
    // User not logged in or has just logged out.
  }
});

.where('userId', '==', userId)

但是我的建议是使用Firebase函数来使用Firestore触发器计算看不见的消息数.因此，在您的函数中，您将执行以下操作

But my suggestion is to use a firebase function to count the number of unseen messages using firestore triggers. So in your function you would do something like

const functions = require('firebase-functions');

exports.countUnseenMessages = functions.firestore
  .document('...')
  .onWrite((change, context) => {
    // increase number of unseen messages to the relevant user
  });

希望有帮助

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