Increment a Firestore document field

Update a Firestore document field using Increment. If a field doesn't exist, Firestore creates the field, and then increments it.

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For detailed documentation that includes this code sample, see the following:

Code sample

C#

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

DocumentReference washingtonRef = db.Collection("cities").Document("DC");

// Atomically increment the population of the city by 50.
await washingtonRef.UpdateAsync("Regions", FieldValue.Increment(50));

Go

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

import (
	"context"
	"fmt"

	"cloud.google.com/go/firestore"
)

// updateDocumentIncrement increments the population of the city document in the
// cities collection by 50.
func updateDocumentIncrement(projectID, city string) error {
	// projectID := "my-project"

	ctx := context.Background()

	client, err := firestore.NewClient(ctx, projectID)
	if err != nil {
		return fmt.Errorf("firestore.NewClient: %w", err)
	}
	defer client.Close()

	dc := client.Collection("cities").Doc(city)
	_, err = dc.Update(ctx, []firestore.Update{
		{Path: "population", Value: firestore.Increment(50)},
	})
	if err != nil {
		return fmt.Errorf("Update: %w", err)
	}

	return nil
}

Java

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

DocumentReference washingtonRef = db.collection("cities").document("DC");

// Atomically increment the population of the city by 50.
final ApiFuture<WriteResult> updateFuture =
    washingtonRef.update("population", FieldValue.increment(50));

Node.js

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

// ...
const washingtonRef = db.collection('cities').doc('DC');

// Atomically increment the population of the city by 50.
const res = await washingtonRef.update({
  population: FieldValue.increment(50)
});

PHP

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

$cityRef = $db->collection('samples/php/cities')->document('DC');

// Atomically increment the population of the city by 50.
$cityRef->update([
    ['path' => 'regions', 'value' => FieldValue::increment(50)]
]);

Python

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

washington_ref = db.collection("cities").document("DC")

washington_ref.update({"population": firestore.Increment(50)})

Ruby

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

city_ref = firestore.doc "#{collection_path}/DC"
city_ref.update({ population: firestore.field_increment(50) })

What's next

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