CODEWITHSUNDEEP
google-cloud-firestoretransactions
wube
wube

Reputation: 1103

Will transaction fail if a document in a sub-collection is modified?

Let's consider the following example:

import { firestore } from 'firebase-admin';

const userCollectionRef = firestore().collection('users');

const setUserData = (userId, data) => {
  return firestore().runTransaction(async trx => {
    const userDocRef = userCollectionRef.doc(userId);
    return trx.set(userDocRef, data);
  });
};

const doSomethingElse = (userId, doc, data) => {
  return userCollectionRef
    .doc(userId)
    .collection('subCollection')
    .doc(doc)
    .set(data);
};

If I call setUserData(123, someData); and while this function is in progress the doSomethingElse(123, 'someDoc', someOtherData) function gets called - will the transaction fail because a document in a sub-collection got modified?

Based on the docs I would assume that transaction will fail only if the user/123 document is modified while setUserData call is in progress, but modifications to user/123/subCollection/someDoc document won't cause the transaction to fail. I'm not sure though because the transaction failure docs section is not very explicit about it. It just says:

The transaction read a document that was modified outside of the transaction. In this case, the transaction automatically runs again. The transaction is retried a finite number of times.

Upvotes: 0

Views: 104

Answers (1)

LeadDreamer
LeadDreamer

Reputation: 3499

While I don't "know" the answer, I can say that documents and documents in their sub-collections are entirely separate - in your example of user/123/subCollection/someDoc, the document user/123 is only used as part of the path/index to user/123/subCollection/someDoc - there is no other relation between them. In fact, document user/123 could be REMOVED and the path to user/123/subCollection/someDoc would remain valid (it shows in Firebase console as an italicized path)

Upvotes: 2

Related Questions