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I have a field which indicates the number of transactions. I would like to increment it by 1 as soon as a transaction occurs. I could'nt find any method to directly execute this.
One method is to get the user first and then update the field with the received value + 1, but this is too lengthy and slow.
Can anyone tell me any other feasible method?
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Firestore Update Document Field What if we want to just update a value of a specific field in an existing document. To do that, all we have to do is add a third argument to the setDoc() method. It will be a JavaScript object with a single property: merge:true.
If you want to gain insight into properties of the collection as a whole, you will need aggregation over a collection. Cloud Firestore does not support native aggregation queries. However, you can use client-side transactions or Cloud Functions to easily maintain aggregate information about your data.
The simple idea is, using a batched write, you write your document to your "data" collection and at the same write to a separate "index" collection where you index the value of the field that you want to be unique.
Firestore now has a specific operator for this called FieldValue.increment(). By applying this operator to a field, the value of that field can be incremented (or decremented) as a single operation on the server.
From the Firebase documentation on incrementing a numeric value:
var washingtonRef = db.collection('cities').doc('DC');
// Atomically increment the population of the city by 50.
washingtonRef.update({ population: firebase.firestore.FieldValue.increment(50) }); So this example increments the population by 50, no matter what is current value is. If the field doesn't exist yet (or is not a number), it is set to 50 in this case.
If you want to decrement a number, pass a negative value to the increment function. For example: firebase.firestore.FieldValue.increment(-50)
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