Can I execute an Firestore query in .then callback of another query?

Question

I am implementing a Cloud Function where I am executing several queries.

    let rating_subcollection = await admin.firestore().collection("restaurants_collection").doc(vendor_id).collection('ratings').where('uID', '==', userId)
    .get()
    .then(async function (data) {            
        if (data.empty) {
            let restaurants_collection = admin.firestore().collection("restaurants_collection").doc(vendor_id);
            await admin.firestore().runTransaction(async (transaction) => {
                const restDoc = await transaction.get(restaurants_collection);

                // Compute new number of ratings
                const newNumRatings = restDoc.data().noRat + 1;

                // Compute new average rating
                const oldRatingTotal = restDoc.data().rat * restDoc.data().noRat;
                const newAvgRating = (oldRatingTotal + ratingVal) / newNumRatings;

                // Update restaurant info
                transaction.update(restaurants_collection, {
                    rat: newAvgRating,
                    noRat: newNumRatings
                });
            })
        }
    }).catch(error => {
        return "Couldnt update the rating: " + error;
    })

So, as you can see I am only executing the transaction IF data is empty and I have set async in the then() callback. Is this the right way to do?!

I'm unclear what the problem is here. If the code works for you, then it's the right thing to do. — Doug Stevenson, Aug 25 '20 at 20:49
Could you share the complete code and point exactly how you want to execute the queries? — Harif Velarde, Aug 28 '20 at 21:40

Harif Velarde · Answer 1 · 2020-08-28T21:43:38.340

I found this example, where is explained on detail how get a collection using an async function, for example if you want to get a collection:

function getValues(collectionName, docName) {
    return db.collection(collectionName).doc(docName).get().then(function (doc) {
        if (doc.exists) return doc.data().text;
        return Promise.reject("No such document");
    }};
}

Or using await it inside an async function in a try/catch block, if you like that better:

async function doSomething() {
    try {
        let text = await getValues('configuration','helpMessage');
        console.log(text);
    } catch {
        console.log("ERROR:" err);
    }
}

Can I execute an Firestore query in .then callback of another query?

1 Answers1