Transacciones y escrituras por lotes

Firestore admite operaciones atómicas para leer y escribir datos. En un conjunto de operaciones atómicas, o bien todas las operaciones se realizan correctamente, o bien no se aplica ninguna. Hay dos tipos de operaciones atómicas en Firestore:

  • Transacciones: una transacción es un conjunto de operaciones de lectura y escritura en uno o varios documentos.
  • Escrituras por lotes: una escritura por lotes es un conjunto de operaciones de escritura en uno o varios documentos.

Actualizar datos con transacciones

Con las bibliotecas de cliente de Firestore, puedes agrupar varias operaciones en una sola transacción. Las transacciones son útiles cuando quieres actualizar el valor de un campo en función de su valor actual o del valor de otro campo.

Una transacción consta de cualquier número de operaciones get() seguidas de cualquier número de operaciones de escritura, como set(), update() o delete(). En el caso de una edición simultánea, Firestore vuelve a ejecutar toda la transacción. Por ejemplo, si una transacción lee documentos y otro cliente modifica alguno de esos documentos, Firestore vuelve a intentar la transacción. Esta función asegura que la transacción se realice con datos actualizados y coherentes.

Las transacciones nunca aplican escrituras de forma parcial. Todas las escrituras se ejecutan al final de una transacción correcta.

Cuando uses transacciones, ten en cuenta lo siguiente:

  • Las operaciones de lectura deben realizarse antes que las de escritura.
  • Una función que llama a una transacción (función de transacción) puede ejecutarse más de una vez si una edición simultánea afecta a un documento que la transacción lee.
  • Las funciones de transacción no deben modificar directamente el estado de la aplicación.
  • Las transacciones fallarán cuando el cliente no tenga conexión.

En el siguiente ejemplo se muestra cómo crear y ejecutar una transacción:

Versión web 9

import { runTransaction } from "firebase/firestore";

try {
  await runTransaction(db, async (transaction) => {
    const sfDoc = await transaction.get(sfDocRef);
    if (!sfDoc.exists()) {
      throw "Document does not exist!";
    }

    const newPopulation = sfDoc.data().population + 1;
    transaction.update(sfDocRef, { population: newPopulation });
  });
  console.log("Transaction successfully committed!");
} catch (e) {
  console.log("Transaction failed: ", e);
}
transaction.js

Versión web 8

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

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

return db.runTransaction((transaction) => {
    // This code may get re-run multiple times if there are conflicts.
    return transaction.get(sfDocRef).then((sfDoc) => {
        if (!sfDoc.exists) {
            throw "Document does not exist!";
        }

        // Add one person to the city population.
        // Note: this could be done without a transaction
        //       by updating the population using FieldValue.increment()
        var newPopulation = sfDoc.data().population + 1;
        transaction.update(sfDocRef, { population: newPopulation });
    });
}).then(() => {
    console.log("Transaction successfully committed!");
}).catch((error) => {
    console.log("Transaction failed: ", error);
});
test.firestore.js
Swift
Nota: Este producto no está disponible en los destinos de watchOS y App Clip. 
let sfReference = db.collection("cities").document("SF")

do {
  let _ = try await db.runTransaction({ (transaction, errorPointer) -> Any? in
    let sfDocument: DocumentSnapshot
    do {
      try sfDocument = transaction.getDocument(sfReference)
    } catch let fetchError as NSError {
      errorPointer?.pointee = fetchError
      return nil
    }

    guard let oldPopulation = sfDocument.data()?["population"] as? Int else {
      let error = NSError(
        domain: "AppErrorDomain",
        code: -1,
        userInfo: [
          NSLocalizedDescriptionKey: "Unable to retrieve population from snapshot \(sfDocument)"
        ]
      )
      errorPointer?.pointee = error
      return nil
    }

    // Note: this could be done without a transaction
    //       by updating the population using FieldValue.increment()
    transaction.updateData(["population": oldPopulation + 1], forDocument: sfReference)
    return nil
  })
  print("Transaction successfully committed!")
} catch {
  print("Transaction failed: \(error)")
}
ViewController.swift
Objective‑C
Nota: Este producto no está disponible en los destinos de watchOS y App Clip. 
FIRDocumentReference *sfReference =
    [[self.db collectionWithPath:@"cities"] documentWithPath:@"SF"];
[self.db runTransactionWithBlock:^id (FIRTransaction *transaction, NSError **errorPointer) {
  FIRDocumentSnapshot *sfDocument = [transaction getDocument:sfReference error:errorPointer];
  if (*errorPointer != nil) { return nil; }

  if (![sfDocument.data[@"population"] isKindOfClass:[NSNumber class]]) {
    *errorPointer = [NSError errorWithDomain:@"AppErrorDomain" code:-1 userInfo:@{
      NSLocalizedDescriptionKey: @"Unable to retreive population from snapshot"
    }];
    return nil;
  }
  NSInteger oldPopulation = [sfDocument.data[@"population"] integerValue];

  // Note: this could be done without a transaction
  //       by updating the population using FieldValue.increment()
  [transaction updateData:@{ @"population": @(oldPopulation + 1) } forDocument:sfReference];

  return nil;
} completion:^(id result, NSError *error) {
  if (error != nil) {
    NSLog(@"Transaction failed: %@", error);
  } else {
    NSLog(@"Transaction successfully committed!");
  }
}];
ViewController.m
Kotlin
Android
val sfDocRef = db.collection("cities").document("SF")

db.runTransaction { transaction ->
    val snapshot = transaction.get(sfDocRef)

    // Note: this could be done without a transaction
    //       by updating the population using FieldValue.increment()
    val newPopulation = snapshot.getDouble("population")!! + 1
    transaction.update(sfDocRef, "population", newPopulation)

    // Success
    null
}.addOnSuccessListener { Log.d(TAG, "Transaction success!") }
    .addOnFailureListener { e -> Log.w(TAG, "Transaction failure.", e) }
DocSnippets.kt
Java
Android
final DocumentReference sfDocRef = db.collection("cities").document("SF");

db.runTransaction(new Transaction.Function<Void>() {
    @Override
    public Void apply(@NonNull Transaction transaction) throws FirebaseFirestoreException {
        DocumentSnapshot snapshot = transaction.get(sfDocRef);

        // Note: this could be done without a transaction
        //       by updating the population using FieldValue.increment()
        double newPopulation = snapshot.getDouble("population") + 1;
        transaction.update(sfDocRef, "population", newPopulation);

        // Success
        return null;
    }
}).addOnSuccessListener(new OnSuccessListener<Void>() {
    @Override
    public void onSuccess(Void aVoid) {
        Log.d(TAG, "Transaction success!");
    }
})
.addOnFailureListener(new OnFailureListener() {
    @Override
    public void onFailure(@NonNull Exception e) {
        Log.w(TAG, "Transaction failure.", e);
    }
});
DocSnippets.java

Dart

final sfDocRef = db.collection("cities").doc("SF");
db.runTransaction((transaction) async {
  final snapshot = await transaction.get(sfDocRef);
  // Note: this could be done without a transaction
  //       by updating the population using FieldValue.increment()
  final newPopulation = snapshot.get("population") + 1;
  transaction.update(sfDocRef, {"population": newPopulation});
}).then(
  (value) => print("DocumentSnapshot successfully updated!"),
  onError: (e) => print("Error updating document $e"),
);
firestore.dart
Java
// Initialize doc
final DocumentReference docRef = db.collection("cities").document("SF");
City city = new City("SF");
city.setCountry("USA");
city.setPopulation(860000L);
docRef.set(city).get();

// run an asynchronous transaction
ApiFuture<Void> futureTransaction =
    db.runTransaction(
        transaction -> {
          // retrieve document and increment population field
          DocumentSnapshot snapshot = transaction.get(docRef).get();
          long oldPopulation = snapshot.getLong("population");
          transaction.update(docRef, "population", oldPopulation + 1);
          return null;
        });
// block on transaction operation using transaction.get()
ManageDataSnippets.java
Python
transaction = db.transaction()
city_ref = db.collection("cities").document("SF")

@firestore.transactional
def update_in_transaction(transaction, city_ref):
    snapshot = city_ref.get(transaction=transaction)
    transaction.update(city_ref, {"population": snapshot.get("population") + 1})

update_in_transaction(transaction, city_ref)
snippets.py
Python
(Async)
transaction = db.transaction()
city_ref = db.collection("cities").document("SF")

@firestore.async_transactional
async def update_in_transaction(transaction, city_ref):
    snapshot = await city_ref.get(transaction=transaction)
    transaction.update(city_ref, {"population": snapshot.get("population") + 1})

await update_in_transaction(transaction, city_ref)
snippets.py
C++
DocumentReference sf_doc_ref = db->Collection("cities").Document("SF");
db->RunTransaction([sf_doc_ref](Transaction& transaction,
                                std::string& out_error_message) -> Error {
    Error error = Error::kErrorOk;

    DocumentSnapshot snapshot =
        transaction.Get(sf_doc_ref, &error, &out_error_message);

    // Note: this could be done without a transaction by updating the
    // population using FieldValue::Increment().
    std::int64_t new_population =
        snapshot.Get("population").integer_value() + 1;
    transaction.Update(
        sf_doc_ref,
        {{"population", FieldValue::Integer(new_population)}});

    return Error::kErrorOk;
  }).OnCompletion([](const Future<void>& future) {
  if (future.error() == Error::kErrorOk) {
    std::cout << "Transaction success!" << std::endl;
  } else {
    std::cout << "Transaction failure: " << future.error_message() << std::endl;
  }
});
snippets.cpp
Node.js
// Initialize document
const cityRef = db.collection('cities').doc('SF');
await cityRef.set({
  name: 'San Francisco',
  state: 'CA',
  country: 'USA',
  capital: false,
  population: 860000
});

try {
  await db.runTransaction(async (t) => {
    const doc = await t.get(cityRef);

    // Add one person to the city population.
    // Note: this could be done without a transaction
    //       by updating the population using FieldValue.increment()
    const newPopulation = doc.data().population + 1;
    t.update(cityRef, {population: newPopulation});
  });

  console.log('Transaction success!');
} catch (e) {
  console.log('Transaction failure:', e);
}
index.js
Go

import (
	"context"
	"log"

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

func runSimpleTransaction(ctx context.Context, client *firestore.Client) error {
	// ...

	ref := client.Collection("cities").Doc("SF")
	err := client.RunTransaction(ctx, func(ctx context.Context, tx *firestore.Transaction) error {
		doc, err := tx.Get(ref) // tx.Get, NOT ref.Get!
		if err != nil {
			return err
		}
		pop, err := doc.DataAt("population")
		if err != nil {
			return err
		}
		return tx.Set(ref, map[string]interface{}{
			"population": pop.(int64) + 1,
		}, firestore.MergeAll)
	})
	if err != nil {
		// Handle any errors appropriately in this section.
		log.Printf("An error has occurred: %s", err)
	}

	return err
}

save_transaction_document_update.go
PHP
$cityRef = $db->collection('samples/php/cities')->document('SF');
$db->runTransaction(function (Transaction $transaction) use ($cityRef) {
    $snapshot = $transaction->snapshot($cityRef);
    $newPopulation = $snapshot['population'] + 1;
    $transaction->update($cityRef, [
        ['path' => 'population', 'value' => $newPopulation]
    ]);
});
transaction_document_update.php
Unity
DocumentReference cityRef = db.Collection("cities").Document("SF");
db.RunTransactionAsync(transaction =>
    {
        return transaction.GetSnapshotAsync(cityRef).ContinueWith((snapshotTask) =>
        {
            DocumentSnapshot snapshot = snapshotTask.Result;
            long newPopulation = snapshot.GetValue<long>("Population") + 1;
            Dictionary<string, object> updates = new Dictionary<string, object>
            {
                { "Population", newPopulation}
            };
            transaction.Update(cityRef, updates);
        });
    });
C#
DocumentReference cityRef = db.Collection("cities").Document("SF");
await db.RunTransactionAsync(async transaction =>
{
    DocumentSnapshot snapshot = await transaction.GetSnapshotAsync(cityRef);
    long newPopulation = snapshot.GetValue<long>("Population") + 1;
    Dictionary<string, object> updates = new Dictionary<string, object>
    {
        { "Population", newPopulation}
    };
    transaction.Update(cityRef, updates);
});
Program.cs
Ruby
city_ref = firestore.doc "#{collection_path}/SF"

firestore.transaction do |tx|
  new_population = tx.get(city_ref).data[:population] + 1
  puts "New population is #{new_population}."
  tx.update city_ref, { population: new_population }
end
transactions_and_batched_writes.rb

Transferir información fuera de las transacciones

No modifiques el estado de la aplicación dentro de las funciones de transacción. Si lo haces, se producirán problemas de simultaneidad, ya que las funciones de transacción se pueden ejecutar varias veces y no se garantiza que se ejecuten en el hilo de la interfaz de usuario. En su lugar, envía la información que necesites desde tus funciones de transacción. En el siguiente ejemplo se toma como base el anterior para mostrar cómo enviar información fuera de una transacción:

Versión web 9

import { doc, runTransaction } from "firebase/firestore";

// Create a reference to the SF doc.
const sfDocRef = doc(db, "cities", "SF");

try {
  const newPopulation = await runTransaction(db, async (transaction) => {
    const sfDoc = await transaction.get(sfDocRef);
    if (!sfDoc.exists()) {
      throw "Document does not exist!";
    }

    const newPop = sfDoc.data().population + 1;
    if (newPop <= 1000000) {
      transaction.update(sfDocRef, { population: newPop });
      return newPop;
    } else {
      return Promise.reject("Sorry! Population is too big");
    }
  });

  console.log("Population increased to ", newPopulation);
} catch (e) {
  // This will be a "population is too big" error.
  console.error(e);
}
transaction_promise.js

Versión web 8

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

db.runTransaction((transaction) => {
    return transaction.get(sfDocRef).then((sfDoc) => {
        if (!sfDoc.exists) {
            throw "Document does not exist!";
        }

        var newPopulation = sfDoc.data().population + 1;
        if (newPopulation <= 1000000) {
            transaction.update(sfDocRef, { population: newPopulation });
            return newPopulation;
        } else {
            return Promise.reject("Sorry! Population is too big.");
        }
    });
}).then((newPopulation) => {
    console.log("Population increased to ", newPopulation);
}).catch((err) => {
    // This will be an "population is too big" error.
    console.error(err);
});
test.firestore.js
Swift
Nota: Este producto no está disponible en los destinos de watchOS y App Clip. 
let sfReference = db.collection("cities").document("SF")

do {
  let object = try await db.runTransaction({ (transaction, errorPointer) -> Any? in
    let sfDocument: DocumentSnapshot
    do {
      try sfDocument = transaction.getDocument(sfReference)
    } catch let fetchError as NSError {
      errorPointer?.pointee = fetchError
      return nil
    }

    guard let oldPopulation = sfDocument.data()?["population"] as? Int else {
      let error = NSError(
        domain: "AppErrorDomain",
        code: -1,
        userInfo: [
          NSLocalizedDescriptionKey: "Unable to retrieve population from snapshot \(sfDocument)"
        ]
      )
      errorPointer?.pointee = error
      return nil
    }

    // Note: this could be done without a transaction
    //       by updating the population using FieldValue.increment()
    let newPopulation = oldPopulation + 1
    guard newPopulation <= 1000000 else {
      let error = NSError(
        domain: "AppErrorDomain",
        code: -2,
        userInfo: [NSLocalizedDescriptionKey: "Population \(newPopulation) too big"]
      )
      errorPointer?.pointee = error
      return nil
    }

    transaction.updateData(["population": newPopulation], forDocument: sfReference)
    return newPopulation
  })
  print("Population increased to \(object!)")
} catch {
  print("Error updating population: \(error)")
}
ViewController.swift
Objective‑C
Nota: Este producto no está disponible en los destinos de watchOS y App Clip. 
FIRDocumentReference *sfReference =
[[self.db collectionWithPath:@"cities"] documentWithPath:@"SF"];
[self.db runTransactionWithBlock:^id (FIRTransaction *transaction, NSError **errorPointer) {
  FIRDocumentSnapshot *sfDocument = [transaction getDocument:sfReference error:errorPointer];
  if (*errorPointer != nil) { return nil; }

  if (![sfDocument.data[@"population"] isKindOfClass:[NSNumber class]]) {
    *errorPointer = [NSError errorWithDomain:@"AppErrorDomain" code:-1 userInfo:@{
      NSLocalizedDescriptionKey: @"Unable to retreive population from snapshot"
    }];
    return nil;
  }
  NSInteger population = [sfDocument.data[@"population"] integerValue];

  population++;
  if (population >= 1000000) {
    *errorPointer = [NSError errorWithDomain:@"AppErrorDomain" code:-2 userInfo:@{
      NSLocalizedDescriptionKey: @"Population too big"
    }];
    return @(population);
  }

  [transaction updateData:@{ @"population": @(population) } forDocument:sfReference];

  return nil;
} completion:^(id result, NSError *error) {
  if (error != nil) {
    NSLog(@"Transaction failed: %@", error);
  } else {
    NSLog(@"Population increased to %@", result);
  }
}];
ViewController.m
Kotlin
Android
val sfDocRef = db.collection("cities").document("SF")

db.runTransaction { transaction ->
    val snapshot = transaction.get(sfDocRef)
    val newPopulation = snapshot.getDouble("population")!! + 1
    if (newPopulation <= 1000000) {
        transaction.update(sfDocRef, "population", newPopulation)
        newPopulation
    } else {
        throw FirebaseFirestoreException(
            "Population too high",
            FirebaseFirestoreException.Code.ABORTED,
        )
    }
}.addOnSuccessListener { result ->
    Log.d(TAG, "Transaction success: $result")
}.addOnFailureListener { e ->
    Log.w(TAG, "Transaction failure.", e)
}
DocSnippets.kt
Java
Android
final DocumentReference sfDocRef = db.collection("cities").document("SF");

db.runTransaction(new Transaction.Function<Double>() {
    @Override
    public Double apply(@NonNull Transaction transaction) throws FirebaseFirestoreException {
        DocumentSnapshot snapshot = transaction.get(sfDocRef);
        double newPopulation = snapshot.getDouble("population") + 1;
        if (newPopulation <= 1000000) {
            transaction.update(sfDocRef, "population", newPopulation);
            return newPopulation;
        } else {
            throw new FirebaseFirestoreException("Population too high",
                    FirebaseFirestoreException.Code.ABORTED);
        }
    }
}).addOnSuccessListener(new OnSuccessListener<Double>() {
    @Override
    public void onSuccess(Double result) {
        Log.d(TAG, "Transaction success: " + result);
    }
})
.addOnFailureListener(new OnFailureListener() {
    @Override
    public void onFailure(@NonNull Exception e) {
        Log.w(TAG, "Transaction failure.", e);
    }
});
DocSnippets.java

Dart

final sfDocRef = db.collection("cities").doc("SF");
db.runTransaction((transaction) {
  return transaction.get(sfDocRef).then((sfDoc) {
    final newPopulation = sfDoc.get("population") + 1;
    transaction.update(sfDocRef, {"population": newPopulation});
    return newPopulation;
  });
}).then(
  (newPopulation) => print("Population increased to $newPopulation"),
  onError: (e) => print("Error updating document $e"),
);
firestore.dart
Java
final DocumentReference docRef = db.collection("cities").document("SF");
ApiFuture<String> futureTransaction =
    db.runTransaction(
        transaction -> {
          DocumentSnapshot snapshot = transaction.get(docRef).get();
          Long newPopulation = snapshot.getLong("population") + 1;
          // conditionally update based on current population
          if (newPopulation <= 1000000L) {
            transaction.update(docRef, "population", newPopulation);
            return "Population increased to " + newPopulation;
          } else {
            throw new Exception("Sorry! Population is too big.");
          }
        });
// Print information retrieved from transaction
System.out.println(futureTransaction.get());
ManageDataSnippets.java
Python
transaction = db.transaction()
city_ref = db.collection("cities").document("SF")

@firestore.transactional
def update_in_transaction(transaction, city_ref):
    snapshot = city_ref.get(transaction=transaction)
    new_population = snapshot.get("population") + 1

    if new_population < 1000000:
        transaction.update(city_ref, {"population": new_population})
        return True
    else:
        return False

result = update_in_transaction(transaction, city_ref)
if result:
    print("Population updated")
else:
    print("Sorry! Population is too big.")
snippets.py
Python
(Async)
transaction = db.transaction()
city_ref = db.collection("cities").document("SF")

@firestore.async_transactional
async def update_in_transaction(transaction, city_ref):
    snapshot = await city_ref.get(transaction=transaction)
    new_population = snapshot.get("population") + 1

    if new_population < 1000000:
        transaction.update(city_ref, {"population": new_population})
        return True
    else:
        return False

result = await update_in_transaction(transaction, city_ref)
if result:
    print("Population updated")
else:
    print("Sorry! Population is too big.")
snippets.py
C++
// This is not yet supported.
Node.js
const cityRef = db.collection('cities').doc('SF');
try {
  const res = await db.runTransaction(async t => {
    const doc = await t.get(cityRef);
    const newPopulation = doc.data().population + 1;
    if (newPopulation <= 1000000) {
      await t.update(cityRef, { population: newPopulation });
      return `Population increased to ${newPopulation}`;
    } else {
      throw 'Sorry! Population is too big.';
    }
  });
  console.log('Transaction success', res);
} catch (e) {
  console.log('Transaction failure:', e);
}
index.js
Go

import (
	"context"
	"errors"
	"log"

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

func infoTransaction(ctx context.Context, client *firestore.Client) (int64, error) {
	var updatedPop int64
	ref := client.Collection("cities").Doc("SF")
	err := client.RunTransaction(ctx, func(ctx context.Context, tx *firestore.Transaction) error {
		doc, err := tx.Get(ref)
		if err != nil {
			return err
		}
		pop, err := doc.DataAt("population")
		if err != nil {
			return err
		}
		newpop := pop.(int64) + 1
		if newpop <= 1000000 {
			err := tx.Set(ref, map[string]interface{}{
				"population": newpop,
			}, firestore.MergeAll)
			if err == nil {
				updatedPop = newpop
			}
			return err
		}
		return errors.New("population is too big")
	})
	if err != nil {
		// Handle any errors in an appropriate way, such as returning them.
		log.Printf("An error has occurred: %s", err)
	}
	return updatedPop, err
}

save_transaction_document_update_conditional.go
PHP
$cityRef = $db->collection('samples/php/cities')->document('SF');
$transactionResult = $db->runTransaction(function (Transaction $transaction) use ($cityRef) {
    $snapshot = $transaction->snapshot($cityRef);
    $newPopulation = $snapshot['population'] + 1;
    if ($newPopulation <= 1000000) {
        $transaction->update($cityRef, [
            ['path' => 'population', 'value' => $newPopulation]
        ]);
        return true;
    } else {
        return false;
    }
});

if ($transactionResult) {
    printf('Population updated successfully.' . PHP_EOL);
} else {
    printf('Sorry! Population is too big.' . PHP_EOL);
}
transaction_document_update_conditional.php
Unity
DocumentReference cityRef = db.Collection("cities").Document("SF");
db.RunTransactionAsync(transaction =>
{
    return transaction.GetSnapshotAsync(cityRef).ContinueWith((task) =>
    {
        long newPopulation = task.Result.GetValue<long>("Population") + 1;
        if (newPopulation <= 1000000)
        {
            Dictionary<string, object> updates = new Dictionary<string, object>
            {
                { "Population", newPopulation}
            };
            transaction.Update(cityRef, updates);
            return true;
        }
        else
        {
            return false;
        } 
    });
}).ContinueWith((transactionResultTask) =>
{
    if (transactionResultTask.Result)
    {
        Console.WriteLine("Population updated successfully.");
    }
    else
    {
        Console.WriteLine("Sorry! Population is too big.");
    } 
});
C#
DocumentReference cityRef = db.Collection("cities").Document("SF");
bool transactionResult = await db.RunTransactionAsync(async transaction =>
{
    DocumentSnapshot snapshot = await transaction.GetSnapshotAsync(cityRef);
    long newPopulation = snapshot.GetValue<long>("Population") + 1;
    if (newPopulation <= 1000000)
    {
        Dictionary<string, object> updates = new Dictionary<string, object>
        {
            { "Population", newPopulation}
        };
        transaction.Update(cityRef, updates);
        return true;
    }
    else
    {
        return false;
    }
});

if (transactionResult)
{
    Console.WriteLine("Population updated successfully.");
}
else
{
    Console.WriteLine("Sorry! Population is too big.");
}
Program.cs
Ruby
city_ref = firestore.doc "#{collection_path}/SF"

updated = firestore.transaction do |tx|
  new_population = tx.get(city_ref).data[:population] + 1
  if new_population < 1_000_000
    tx.update city_ref, { population: new_population }
    true
  end
end

if updated
  puts "Population updated!"
else
  puts "Sorry! Population is too big."
end
transactions_and_batched_writes.rb

Fallo de transacción

Una transacción puede fallar por los siguientes motivos:

  • La transacción contiene operaciones de lectura después de operaciones de escritura. Las operaciones de lectura siempre deben realizarse antes que las de escritura.
  • La transacción ha leído un documento que se ha modificado fuera de la transacción. En ese caso, la transacción se vuelve a ejecutar automáticamente. La transacción se vuelve a intentar un número finito de veces.

  • La transacción ha superado el tamaño máximo de solicitud de 10 MiB.

    El tamaño de la transacción depende del tamaño de los documentos y las entradas de índice modificados por la transacción. En el caso de una operación de eliminación, se incluye el tamaño del documento de destino y los tamaños de las entradas de índice eliminadas en respuesta a la operación.

  • La transacción ha superado el plazo de bloqueo (20 segundos). Firestore libera automáticamente los bloqueos si una transacción no se puede completar a tiempo.

Una transacción fallida devuelve un error y no escribe nada en la base de datos. No es necesario que reviertas la transacción, ya que Firestore lo hace automáticamente.

Escrituras por lotes

Si no necesitas leer ningún documento en tu conjunto de operaciones, puedes ejecutar varias operaciones de escritura como un único lote que contenga cualquier combinación de operaciones set(), update() o delete(). Cada operación del lote se contabiliza por separado en el uso de Firestore. Un lote de escrituras se completa de forma atómica y puede escribir en varios documentos. En el siguiente ejemplo se muestra cómo crear y confirmar un lote de escritura:

Versión web 9

import { writeBatch, doc } from "firebase/firestore"; 

// Get a new write batch
const batch = writeBatch(db);

// Set the value of 'NYC'
const nycRef = doc(db, "cities", "NYC");
batch.set(nycRef, {name: "New York City"});

// Update the population of 'SF'
const sfRef = doc(db, "cities", "SF");
batch.update(sfRef, {"population": 1000000});

// Delete the city 'LA'
const laRef = doc(db, "cities", "LA");
batch.delete(laRef);

// Commit the batch
await batch.commit();
write_batch.js

Versión web 8

// Get a new write batch
var batch = db.batch();

// Set the value of 'NYC'
var nycRef = db.collection("cities").doc("NYC");
batch.set(nycRef, {name: "New York City"});

// Update the population of 'SF'
var sfRef = db.collection("cities").doc("SF");
batch.update(sfRef, {"population": 1000000});

// Delete the city 'LA'
var laRef = db.collection("cities").doc("LA");
batch.delete(laRef);

// Commit the batch
batch.commit().then(() => {
    // ...
});
test.firestore.js
Swift
Nota: Este producto no está disponible en los destinos de watchOS y App Clip. 
// Get new write batch
let batch = db.batch()

// Set the value of 'NYC'
let nycRef = db.collection("cities").document("NYC")
batch.setData([:], forDocument: nycRef)

// Update the population of 'SF'
let sfRef = db.collection("cities").document("SF")
batch.updateData(["population": 1000000 ], forDocument: sfRef)

// Delete the city 'LA'
let laRef = db.collection("cities").document("LA")
batch.deleteDocument(laRef)

// Commit the batch
do {
  try await batch.commit()
  print("Batch write succeeded.")
} catch {
  print("Error writing batch: \(error)")
}
ViewController.swift
Objective‑C
Nota: Este producto no está disponible en los destinos de watchOS y App Clip. 
// Get new write batch
FIRWriteBatch *batch = [self.db batch];

// Set the value of 'NYC'
FIRDocumentReference *nycRef =
    [[self.db collectionWithPath:@"cities"] documentWithPath:@"NYC"];
[batch setData:@{} forDocument:nycRef];

// Update the population of 'SF'
FIRDocumentReference *sfRef =
    [[self.db collectionWithPath:@"cities"] documentWithPath:@"SF"];
[batch updateData:@{ @"population": @1000000 } forDocument:sfRef];

// Delete the city 'LA'
FIRDocumentReference *laRef =
    [[self.db collectionWithPath:@"cities"] documentWithPath:@"LA"];
[batch deleteDocument:laRef];

// Commit the batch
[batch commitWithCompletion:^(NSError * _Nullable error) {
  if (error != nil) {
    NSLog(@"Error writing batch %@", error);
  } else {
    NSLog(@"Batch write succeeded.");
  }
}];
ViewController.m
Kotlin
Android
val nycRef = db.collection("cities").document("NYC")
val sfRef = db.collection("cities").document("SF")
val laRef = db.collection("cities").document("LA")

// Get a new write batch and commit all write operations
db.runBatch { batch ->
    // Set the value of 'NYC'
    batch.set(nycRef, City())

    // Update the population of 'SF'
    batch.update(sfRef, "population", 1000000L)

    // Delete the city 'LA'
    batch.delete(laRef)
}.addOnCompleteListener {
    // ...
}
DocSnippets.kt
Java
Android
// Get a new write batch
WriteBatch batch = db.batch();

// Set the value of 'NYC'
DocumentReference nycRef = db.collection("cities").document("NYC");
batch.set(nycRef, new City());

// Update the population of 'SF'
DocumentReference sfRef = db.collection("cities").document("SF");
batch.update(sfRef, "population", 1000000L);

// Delete the city 'LA'
DocumentReference laRef = db.collection("cities").document("LA");
batch.delete(laRef);

// Commit the batch
batch.commit().addOnCompleteListener(new OnCompleteListener<Void>() {
    @Override
    public void onComplete(@NonNull Task<Void> task) {
        // ...
    }
});
DocSnippets.java

Dart

// Get a new write batch
final batch = db.batch();

// Set the value of 'NYC'
var nycRef = db.collection("cities").doc("NYC");
batch.set(nycRef, {"name": "New York City"});

// Update the population of 'SF'
var sfRef = db.collection("cities").doc("SF");
batch.update(sfRef, {"population": 1000000});

// Delete the city 'LA'
var laRef = db.collection("cities").doc("LA");
batch.delete(laRef);

// Commit the batch
batch.commit().then((_) {
  // ...
});
firestore.dart
Java
// Get a new write batch
WriteBatch batch = db.batch();

// Set the value of 'NYC'
DocumentReference nycRef = db.collection("cities").document("NYC");
batch.set(nycRef, new City());

// Update the population of 'SF'
DocumentReference sfRef = db.collection("cities").document("SF");
batch.update(sfRef, "population", 1000000L);

// Delete the city 'LA'
DocumentReference laRef = db.collection("cities").document("LA");
batch.delete(laRef);

// asynchronously commit the batch
ApiFuture<List<WriteResult>> future = batch.commit();
// ...
// future.get() blocks on batch commit operation
for (WriteResult result : future.get()) {
  System.out.println("Update time : " + result.getUpdateTime());
}
ManageDataSnippets.java
Python
batch = db.batch()

# Set the data for NYC
nyc_ref = db.collection("cities").document("NYC")
batch.set(nyc_ref, {"name": "New York City"})

# Update the population for SF
sf_ref = db.collection("cities").document("SF")
batch.update(sf_ref, {"population": 1000000})

# Delete DEN
den_ref = db.collection("cities").document("DEN")
batch.delete(den_ref)

# Commit the batch
batch.commit()
snippets.py
Python
(Async)
batch = db.batch()

# Set the data for NYC
nyc_ref = db.collection("cities").document("NYC")
batch.set(nyc_ref, {"name": "New York City"})

# Update the population for SF
sf_ref = db.collection("cities").document("SF")
batch.update(sf_ref, {"population": 1000000})

# Delete DEN
den_ref = db.collection("cities").document("DEN")
batch.delete(den_ref)

# Commit the batch
await batch.commit()
snippets.py
C++
// Get a new write batch
WriteBatch batch = db->batch();

// Set the value of 'NYC'
DocumentReference nyc_ref = db->Collection("cities").Document("NYC");
batch.Set(nyc_ref, {});

// Update the population of 'SF'
DocumentReference sf_ref = db->Collection("cities").Document("SF");
batch.Update(sf_ref, {{"population", FieldValue::Integer(1000000)}});

// Delete the city 'LA'
DocumentReference la_ref = db->Collection("cities").Document("LA");
batch.Delete(la_ref);

// Commit the batch
batch.Commit().OnCompletion([](const Future<void>& future) {
  if (future.error() == Error::kErrorOk) {
    std::cout << "Write batch success!" << std::endl;
  } else {
    std::cout << "Write batch failure: " << future.error_message() << std::endl;
  }
});
snippets.cpp
Node.js
// Get a new write batch
const batch = db.batch();

// Set the value of 'NYC'
const nycRef = db.collection('cities').doc('NYC');
batch.set(nycRef, {name: 'New York City'});

// Update the population of 'SF'
const sfRef = db.collection('cities').doc('SF');
batch.update(sfRef, {population: 1000000});

// Delete the city 'LA'
const laRef = db.collection('cities').doc('LA');
batch.delete(laRef);

// Commit the batch
await batch.commit();
index.js
Go

import (
	"context"
	"log"

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

func batchWrite(ctx context.Context, client *firestore.Client) error {
	// Get a new write batch.
	batch := client.Batch()

	// Set the value of "NYC".
	nycRef := client.Collection("cities").Doc("NYC")
	batch.Set(nycRef, map[string]interface{}{
		"name": "New York City",
	})

	// Update the population of "SF".
	sfRef := client.Collection("cities").Doc("SF")
	batch.Set(sfRef, map[string]interface{}{
		"population": 1000000,
	}, firestore.MergeAll)

	// Delete the city "LA".
	laRef := client.Collection("cities").Doc("LA")
	batch.Delete(laRef)

	// Commit the batch.
	_, err := batch.Commit(ctx)
	if err != nil {
		// Handle any errors in an appropriate way, such as returning them.
		log.Printf("An error has occurred: %s", err)
	}

	return err
}

save_data_batch_writes.go
PHP
$batch = $db->batch();

# Set the data for NYC
$nycRef = $db->collection('samples/php/cities')->document('NYC');
$batch->set($nycRef, [
    'name' => 'New York City'
]);

# Update the population for SF
$sfRef = $db->collection('samples/php/cities')->document('SF');
$batch->update($sfRef, [
    ['path' => 'population', 'value' => 1000000]
]);

# Delete LA
$laRef = $db->collection('samples/php/cities')->document('LA');
$batch->delete($laRef);

# Commit the batch
$batch->commit();
data_batch_writes.php
Unity
WriteBatch batch = db.StartBatch();

// Set the data for NYC
DocumentReference nycRef = db.Collection("cities").Document("NYC");
Dictionary<string, object> nycData = new Dictionary<string, object>
{
    { "name", "New York City" }
};
batch.Set(nycRef, nycData);

// Update the population for SF
DocumentReference sfRef = db.Collection("cities").Document("SF");
Dictionary<string, object> updates = new Dictionary<string, object>
{
    { "Population", 1000000}
};
batch.Update(sfRef, updates);

// Delete LA
DocumentReference laRef = db.Collection("cities").Document("LA");
batch.Delete(laRef);

// Commit the batch
batch.CommitAsync();
C#
WriteBatch batch = db.StartBatch();

// Set the data for NYC
DocumentReference nycRef = db.Collection("cities").Document("NYC");
Dictionary<string, object> nycData = new Dictionary<string, object>
{
    { "name", "New York City" }
};
batch.Set(nycRef, nycData);

// Update the population for SF
DocumentReference sfRef = db.Collection("cities").Document("SF");
Dictionary<string, object> updates = new Dictionary<string, object>
{
    { "Population", 1000000}
};
batch.Update(sfRef, updates);

// Delete LA
DocumentReference laRef = db.Collection("cities").Document("LA");
batch.Delete(laRef);

// Commit the batch
await batch.CommitAsync();
Program.cs
Ruby
firestore.batch do |b|
  # Set the data for NYC
  b.set "#{collection_path}/NYC", { name: "New York City" }

  # Update the population for SF
  b.update "#{collection_path}/SF", { population: 1_000_000 }

  # Delete LA
  b.delete "#{collection_path}/LA"
end
transactions_and_batched_writes.rb

Al igual que las transacciones, las escrituras por lotes son atómicas. A diferencia de las transacciones, las escrituras por lotes no tienen que asegurarse de que los documentos leídos no se modifiquen, lo que conlleva menos casos de error. No están sujetos a reintentos ni a errores por demasiados reintentos. Las escrituras por lotes se ejecutan incluso cuando el dispositivo del usuario no tiene conexión.

Una escritura por lotes con cientos de documentos puede requerir muchas actualizaciones de índice y superar el límite de tamaño de las transacciones. En este caso, reduce el número de documentos por lote. Si quieres escribir un gran número de documentos, te recomendamos que utilices un writer masivo o escrituras individuales paralelizadas.

Validación de datos para operaciones atómicas

En el caso de las bibliotecas de cliente web o para móviles, puedes validar los datos con las reglas de seguridad de Firestore. Puedes asegurarte de que los documentos relacionados se actualicen siempre de forma atómica y siempre como parte de una transacción o de una escritura por lotes. Usa la función de regla de seguridad getAfter() para acceder y validar el estado de un documento después de que se complete un conjunto de operaciones, pero antes de que Firestore confirme las operaciones.

Por ejemplo, supongamos que la base de datos del ejemplo cities también contiene una colección countries. Cada documento country usa un campo last_updated para registrar la última vez que se actualizó alguna ciudad relacionada con ese país. Las siguientes reglas de seguridad requieren que, al actualizar un documento city, también se actualice de forma atómica el campo last_updated del país correspondiente:

service cloud.firestore {
  match /databases/{database}/documents {
    // If you update a city doc, you must also
    // update the related country's last_updated field.
    match /cities/{city} {
      allow write: if request.auth != null &&
        getAfter(
          /databases/$(database)/documents/countries/$(request.resource.data.country)
        ).data.last_updated == request.time;
    }

    match /countries/{country} {
      allow write: if request.auth != null;
    }
  }
}

Límites de las reglas de seguridad

En las reglas de seguridad de las transacciones o las escrituras por lotes, hay un límite de 20 llamadas de acceso al documento para toda la operación atómica, además del límite normal de 10 llamadas para cada operación de un solo documento del lote.

Por ejemplo, considera las siguientes reglas para una aplicación de chat:

service cloud.firestore {
  match /databases/{db}/documents {
    function prefix() {
      return /databases/{db}/documents;
    }
    match /chatroom/{roomId} {
      allow read, write: if request.auth != null && roomId in get(/$(prefix())/users/$(request.auth.uid)).data.chats
                            || exists(/$(prefix())/admins/$(request.auth.uid));
    }
    match /users/{userId} {
      allow read, write: if request.auth != null && request.auth.uid == userId
                            || exists(/$(prefix())/admins/$(request.auth.uid));
    }
    match /admins/{userId} {
      allow read, write: if request.auth != null && exists(/$(prefix())/admins/$(request.auth.uid));
    }
  }
}

Los fragmentos de código que se muestran a continuación ilustran el número de llamadas de acceso a documentos que se han usado en algunos patrones de acceso a datos:

// 0 document access calls used, because the rules evaluation short-circuits
// before the exists() call is invoked.
db.collection('user').doc('myuid').get(...);

// 1 document access call used. The maximum total allowed for this call
// is 10, because it is a single document request.
db.collection('chatroom').doc('mygroup').get(...);

// Initializing a write batch...
var batch = db.batch();

// 2 document access calls used, 10 allowed.
var group1Ref = db.collection("chatroom").doc("group1");
batch.set(group1Ref, {msg: "Hello, from Admin!"});

// 1 document access call used, 10 allowed.
var newUserRef = db.collection("users").doc("newuser");
batch.update(newUserRef, {"lastSignedIn": new Date()});

// 1 document access call used, 10 allowed.
var removedAdminRef = db.collection("admin").doc("otheruser");
batch.delete(removedAdminRef);

// The batch used a total of 2 + 1 + 1 = 4 document access calls, out of a total
// 20 allowed.
batch.commit();

Para obtener más información sobre cómo resolver problemas de latencia causados por escrituras grandes y por lotes, errores debidos a la contención de transacciones superpuestas y otros problemas, consulta la página de solución de problemas.