javascript - 在 firebase 中同时更新数组

Question

.runTransaction(async transaction => {
    const newContractUid = uuid();
    const newContractRef = firestore
        .collection(COLLECTION_CONTRACTS)
        .doc(newContractUid);
    const creatorRef = firestore.collection(COLLECTION_USERS).doc(creatorId);
    const recipientRef = firestore
        .collection(COLLECTION_USERS)
        .doc(recipientId);
    const [creator, recipient, newContractDoc] = [
        await transaction.get(creatorRef),
        await transaction.get(recipientRef),
        await transaction.get(newContractRef)
    ];
    if (newContractDoc.exists) {
        console.warn("Attempted to create contract with already taked UUID");
        return Promise.reject(
            "Attempted to create contract with already taken UUID"
        );
    }
    contractData.creationDate = Date.now().toString();

    transaction.set(newContractRef, contractData);
    // Update recipient and creator with contract relations
    transaction.update(creatorRef, {
        contracts: _.concat(creator.data().contracts, newContractUid)
    });
    transaction.update(recipientRef, {
        contracts: _.concat(recipient.data().contracts, newContractUid)
    });
})

我有这段代码可以在我的 firestore 中创建一个新契约(Contract)。然后它将此契约(Contract)与两个用户(创建者和接收者)相关联。

但是我担心这行代码:

transaction.update(creatorRef, {
    contracts: _.concat(creator.data().contracts, newContractUid)
});

是否有可能另一个用户在交易发生时写入 creator.data() 字段并使我的数据在此处无效。或者我在交易期间是否有写锁？

编辑:

嗯，我在 firebase 文档中看到了这个

For example, if a transaction reads documents and another client modifies any of those documents, Cloud Firestore retries the transaction. This feature ensures that the transaction runs on up-to-date and consistent data.

我认为这意味着我在这种情况下是安全的，但我不确定

Answer 1

Firestore 事务可防止并发写入。如果它检测到写入冲突，它会重试事务，因此您的事务处理程序可能会为单个写入操作调用多次。