fetch and modify data simultaneously in firebase

Question

fetch and modify data simultaneously in firebase

Is there a way to retrieve a value from a Firebase document and immediately update it?

I am familiar with methods for updating documents and retrieving their values separately, but how can I accomplish both in one go?

update

firebase.firestore().collection("colection").doc('document').set(
 {
      value: value + 10

  }, { merge: true })

get

firebase.firestore().collection("colection").doc("document").get().then((doc) => {
        if (doc.exists) {
            console.log("Document data:", doc.data().value);
        } else {
            console.log("No such document!");
        }
    }).catch((error) => {
        console.log("Error getting document:", error);
    });

javascript firebase google-cloud-firestore

Answer 1

Answer №1

If you need to perform atomic read-and-update operations on a document, the recommended approach is to utilize a transaction. An example from the official documentation illustrates this concept:

// Create a reference to the LA doc.
var laDocRef = db.collection("cities").doc("LA");

// Uncomment to initialize the doc.
// laDocRef.set({ population: 0 });

return db.runTransaction((transaction) => {
    // This code might be executed multiple times in case of conflicts.
    return transaction.get(laDocRef).then((laDoc) => {
        if (!laDoc.exists) {
            throw "Document doesn't exist!";
        }

        // Increase the city's population by one person.
        // Note: this operation could be performed without a transaction
        // by updating the population using FieldValue.increment()
        var newPopulation = laDoc.data().population + 1;
        transaction.update(laDocRef, { population: newPopulation });
    });
}).then(() => {
    console.log("Transaction successfully completed!");
}).catch((error) => {
    console.log("Transaction failed: ", error);
});

Answer 2

If you need to perform atomic read-and-update operations on a document, the recommended approach is to utilize a transaction. An example from the official documentation illustrates this concept:

// Create a reference to the LA doc.
var laDocRef = db.collection("cities").doc("LA");

// Uncomment to initialize the doc.
// laDocRef.set({ population: 0 });

return db.runTransaction((transaction) => {
    // This code might be executed multiple times in case of conflicts.
    return transaction.get(laDocRef).then((laDoc) => {
        if (!laDoc.exists) {
            throw "Document doesn't exist!";
        }

        // Increase the city's population by one person.
        // Note: this operation could be performed without a transaction
        // by updating the population using FieldValue.increment()
        var newPopulation = laDoc.data().population + 1;
        transaction.update(laDocRef, { population: newPopulation });
    });
}).then(() => {
    console.log("Transaction successfully completed!");
}).catch((error) => {
    console.log("Transaction failed: ", error);
});

fetch and modify data simultaneously in firebase

Answer №1

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