Cloud Functions using wildcard path don't work

Question

I try to update all documents in a collection with a Cloud Function. With this code it worked for updating one document (with the id 0) in the collection releasedQuestions:

exports.decreaseQuestionRestDuration = functions.https.onRequest((request, response) => {
   const test = admin.firestore().doc('releasedQuestions/0').update({restDuration: 42})
        .then(snapshot => {
            response.send(0)
        })
        .catch(error => {
            console.log(error)
            response.status(500).send(error)
        })
});

but when i will update all documents in the collection with a wildcard path like this:

const test = admin.firestore().doc('releasedQuestions/{qid}').update({restDuration: 42})

it doesn't work. Can anyone help me?

My Cloud Firestore structure is this: Cloud Firestore structure

Answer 1

The wildcard path syntax you are using (i.e. doc('releasedQuestions/{qid}')) can only be used in Cloud Functions definition, when, for example, you define a Cloud Firestore trigger by specifying a document path and an event type, as follows:

exports.useWildcard = functions.firestore
    .document('users/{userId}')
    .onWrite((change, context) => {...});

In your case you are actually calling the doc() method, for which the documentPath parameter shall be a string. This is why it works in the first case but not in the second one (there isn't any Firestore document with ID {qid} in your collection).

---

If you want, in your HTTP Cloud Function, to update all the docs of a collection, you could use a batched write, as follows:

exports.decreaseQuestionRestDuration = functions.https.onRequest((request, response) => {

    const db = admin.firestore();

    db.collection('releasedQuestions').get()
        .then(snapshot => {
            let batch = db.batch();
            snapshot.forEach(doc => {
                batch.update(doc.ref, { restDuration: 42 });
            });
            return batch.commit()
        })
        .then(() => {
            response.send(0)
        })
        .catch(error => {
            console.log(error)
            response.status(500).send(error)
        })

});

---

Note however, that a batched write can contain up to 500 operations. Therefore, if your collection contains more than 500 documents, you may use Promise.all() instead.

---

As a side note, it's worth noting the existence of Template literals.

Template literals are enclosed by the backtick (grave accent) character instead of double or single quotes... and can contain placeholders.