Firebase:事务读取和更新多个文档 [英] Firebase: Transaction read and update multiple documents

问题描述

使用此代码，我可以读取和更新交易中的单个文档.

With this code I can read and update single document in the transaction.

// Update likes in post
var docRef = admin
  .firestore()
  .collection("posts")
  .doc(doc_id);

let post = await admin.firestore().runTransaction(t => t.get(docRef));
if (!post.exists) {
  console.log("post not exist")
}
postData = { ...post.data(), id: post.id };
let likes = postData.likes || 0;
var newLikes = likes + 1;
await post.ref.update({ likes: newLikes });

问题:但是我需要阅读和更新多个文档，每个文档都根据其内容进行更新.例如，我想像我的代码一样更新帖子集合中的点赞次数，但也要更新个人资料文档中的总点赞次数.

Question: But I need to read and update multiple documents and each one update depending on their content. For example I want to update number of likes in posts collection as in my code but also update number of total likes in my profile document.

推荐答案

要更新事务中的多个文档，请多次调用 t.update().

To update multiple documents in a transaction, you call t.update() multiple times.

let promise = await admin.firestore().runTransaction(transaction => {
  var post = transaction.get(docRef);
  var anotherPost = transaction.get(anotherDocRef);

  if (post.exists && anotherPost.exists) {
    var newLikes = (post.data().likes || 0) + 1;
    await transaction.update(docRef, { likes: newLikes });
    newLikes = (anotherPost.data().likes || 0) + 1;
    await transaction.update(anotherdocRef, { likes: newLikes });
  }
})

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

这篇关于Firebase:事务读取和更新多个文档的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！