Firebase Firestore事务错误:无法修改已提交的WriteBatch

问题描述

我正在云功能上进行部署，并出现此错误

I am deploying on cloud functions, and getting this error

Error: Cannot modify a WriteBatch that has been committed.
at WriteBatch.verifyNotCommitted (/user_code/node_modules/firebase-admin/node_modules/@google-cloud/firestore/build/src/write-batch.js:112:19)
at WriteBatch.update (/user_code/node_modules/firebase-admin/node_modules/@google-cloud/firestore/build/src/write-batch.js:299:14)
at Transaction.update (/user_code/node_modules/firebase-admin/node_modules/@google-cloud/firestore/build/src/transaction.js:225:33)
at transaction.get.then (/user_code/index.js:22:40)
at process._tickDomainCallback (internal/process/next_tick.js:135:7)

下面是我的代码，我正在使用事务在Firestore上进行更新和删除.

Below is my code, I am using transaction to update and delete on Firestore.

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

 const admin = require('firebase-admin');
 admin.initializeApp();
   const firestore = admin.firestore();

  exports.updateUserSize = functions.auth.user().onDelete((user) => {
var userDocRef = firestore.collection("users").where('uid', '==', 
 user.uid).limit(1);

return firestore.runTransaction(function(transaction) {
    return transaction.get(userDocRef).then((snapshot) => {
        snapshot.forEach(userDoc => {
            if (!userDoc.exists) {
                throw "userDoc does not exist!";
            }
            console.log("user_uid: " + userDoc.data().uid + " | instanceDocId: " + userDoc.data().instance);

            var instanceDocRef = firestore.collection("utils").doc(userDoc.data().instance);
            return transaction.get(instanceDocRef).then((snapshot) => {
                console.log("snapshotn: " + snapshot.data().user_size);
                var newUserSize = snapshot.data().user_size - 1;
                transaction.update(instanceDocRef, { user_size: newUserSize });
            });
        });
    });    

}).then(function() {
    console.log("Transaction successfully committed!");
}).catch(function(error) {
    console.log("Transaction failed: ", error);
});
 });

任何帮助将不胜感激.

推荐答案

这是通过使用for循环解决的，如@Renaud Tarnec在评论中所述.

This was solved by using a for loop, as mentioned by @Renaud Tarnec in the comments.

我认为您的问题来自以下事实:您将transaction多次返回到forEach循环中.同样，您在执行transaction.update(instanceDocRef, { user_size: newUserSize });时也不会返回事务.谨建议您详细研究文档: https://firebase. google.com/docs/firestore/manage-data/transactions 和