Daten mit Aggregationsabfragen zusammenfassen
Bei einer Aggregationsabfrage werden die Daten aus mehreren Indexeinträgen verarbeitet, um einen einzelnen Zusammenfassungswert zurückzugeben.
Firestore unterstützt die folgenden Aggregationsabfragen:
count()
sum()
average()
Firestore berechnet die Aggregation und überträgt nur das Ergebnis an Ihre Anwendung zurück. Im Vergleich zum Ausführen einer vollständigen Abfrage und Berechnen der Aggregation in Ihrer Anwendung sparen Aggregationsabfragen sowohl das Lesen abgerechneter Dokumente als auch die übertragenen Byte ein.
Aggregationsabfragen basieren auf der vorhandenen Indexkonfiguration, die von Ihren Abfragen bereits verwendet wird, und werden proportional zur Anzahl der gescannten Indexeinträge skaliert. Die Latenz nimmt mit der Anzahl der Elemente in der Aggregation zu.
Aggregationsmethode count()
verwenden
Mit der Aggregationsabfrage count()
können Sie die Anzahl der Dokumente in einer Sammlung oder Abfrage ermitteln.
Sehen Sie sich die Beispieldaten an, die wir unter Daten abrufen eingerichtet haben.
Die folgende Aggregation count()
gibt die Gesamtzahl der Städte in der Sammlung cities
zurück.
Webversion 9
const coll = collection(db, "cities"); const snapshot = await getCountFromServer(coll); console.log('count: ', snapshot.data().count);
Swift
let query = db.collection("cities") let countQuery = query.count do { let snapshot = try await countQuery.getAggregation(source: .server) print(snapshot.count) } catch { print(error) }
Objective-C
FIRCollectionReference *query = [self.db collectionWithPath:@"cities"]; [query.count aggregationWithSource:FIRAggregateSourceServer completion:^(FIRAggregateQuerySnapshot *snapshot, NSError *error) { if (error != nil) { NSLog(@"Error fetching count: %@", error); } else { NSLog(@"Cities count: %@", snapshot.count); } }];
Java
Android
Query query = db.collection("cities"); AggregateQuery countQuery = query.count(); countQuery.get(AggregateSource.SERVER).addOnCompleteListener(new OnCompleteListener<AggregateQuerySnapshot>() { @Override public void onComplete(@NonNull Task<AggregateQuerySnapshot> task) { if (task.isSuccessful()) { // Count fetched successfully AggregateQuerySnapshot snapshot = task.getResult(); Log.d(TAG, "Count: " + snapshot.getCount()); } else { Log.d(TAG, "Count failed: ", task.getException()); } } });
Kotlin+KTX
Android
val query = db.collection("cities") val countQuery = query.count() countQuery.get(AggregateSource.SERVER).addOnCompleteListener { task -> if (task.isSuccessful) { // Count fetched successfully val snapshot = task.result Log.d(TAG, "Count: ${snapshot.count}") } else { Log.d(TAG, "Count failed: ", task.getException()) } }
Dart
// Returns number of documents in users collection db.collection("users").count().get().then( (res) => print(res.count), onError: (e) => print("Error completing: $e"), );
Einfach loslegen (Go)
Java
CollectionReference collection = db.collection("cities"); AggregateQuerySnapshot snapshot = collection.count().get().get(); System.out.println("Count: " + snapshot.getCount());
Node.js
const collectionRef = db.collection('cities'); const snapshot = await collectionRef.count().get(); console.log(snapshot.data().count);
Python
Die Aggregation count()
berücksichtigt alle Filter in der Abfrage und alle limit
-Klauseln.
Webversion 9
const coll = collection(db, "cities"); const q = query(coll, where("state", "==", "CA")); const snapshot = await getCountFromServer(q); console.log('count: ', snapshot.data().count);
Swift
let query = db.collection("cities").whereField("state", isEqualTo: "CA") let countQuery = query.count do { let snapshot = try await countQuery.getAggregation(source: .server) print(snapshot.count) } catch { print(error) }
Objective-C
FIRQuery *query = [[self.db collectionWithPath:@"cities"] queryWhereField:@"state" isEqualTo:@"CA"]; [query.count aggregationWithSource:FIRAggregateSourceServer completion:^(FIRAggregateQuerySnapshot *snapshot, NSError *error) { if (error != nil) { NSLog(@"Error fetching count: %@", error); } else { NSLog(@"Cities count: %@", snapshot.count); } }];
Java
Android
Query query = db.collection("cities").whereEqualTo("state", "CA"); AggregateQuery countQuery = query.count(); countQuery.get(AggregateSource.SERVER).addOnCompleteListener(new OnCompleteListener<AggregateQuerySnapshot>() { @Override public void onComplete(@NonNull Task<AggregateQuerySnapshot> task) { if (task.isSuccessful()) { // Count fetched successfully AggregateQuerySnapshot snapshot = task.getResult(); Log.d(TAG, "Count: " + snapshot.getCount()); } else { Log.d(TAG, "Count failed: ", task.getException()); } } });
Kotlin+KTX
Android
val query = db.collection("cities").whereEqualTo("state", "CA") val countQuery = query.count() countQuery.get(AggregateSource.SERVER).addOnCompleteListener { task -> if (task.isSuccessful) { // Count fetched successfully val snapshot = task.result Log.d(TAG, "Count: ${snapshot.count}") } else { Log.d(TAG, "Count failed: ", task.getException()) } }
Dart
// This also works with collectionGroup queries. db.collection("users").where("age", isGreaterThan: 10).count().get().then( (res) => print(res.count), onError: (e) => print("Error completing: $e"), );
Einfach loslegen (Go)
Java
CollectionReference collection = db.collection("cities"); Query query = collection.whereEqualTo("state", "CA"); AggregateQuerySnapshot snapshot = query.count().get().get(); System.out.println("Count: " + snapshot.getCount());
Node.js
const collectionRef = db.collection('cities'); const query = collectionRef.where('state', '==', 'CA'); const snapshot = await query.count().get(); console.log(snapshot.data().count);
Python
Aggregationsmethode sum()
verwenden
Verwenden Sie die Aggregation sum()
, um die Gesamtsumme der numerischen Werte zurückzugeben, die einer bestimmten Abfrage entsprechen. Beispiel:
Webversion 9
const coll = collection(firestore, 'cities'); const snapshot = await getAggregateFromServer(coll, { totalPopulation: sum('population') }); console.log('totalPopulation: ', snapshot.data().totalPopulation);
Swift
let query = db.collection("cities") let aggregateQuery = query.aggregate([AggregateField.sum("population")]) do { let snapshot = try await aggregateQuery.getAggregation(source: .server) print(snapshot.get(AggregateField.sum("population"))) } catch { print(error) }
Objective-C
FIRQuery *query = [self.db collectionWithPath:@"cities"]; FIRAggregateQuery *aggregateQuery = [query aggregate:@[ [FIRAggregateField aggregateFieldForSumOfField:@"population"]]]; [aggregateQuery aggregationWithSource:FIRAggregateSourceServer completion:^(FIRAggregateQuerySnapshot *snapshot, NSError *error) { if (error != nil) { NSLog(@"Error fetching aggregate: %@", error); } else { NSLog(@"Sum: %@", [snapshot valueForAggregateField:[FIRAggregateField aggregateFieldForSumOfField:@"population"]]); } }];
Java
Android
Query query = db.collection("cities"); AggregateQuery aggregateQuery = query.aggregate(AggregateField.sum("population")); aggregateQuery.get(AggregateSource.SERVER).addOnCompleteListener(new OnCompleteListener<AggregateQuerySnapshot>() { @Override public void onComplete(@NonNull Task<AggregateQuerySnapshot> task) { if (task.isSuccessful()) { // Aggregate fetched successfully AggregateQuerySnapshot snapshot = task.getResult(); Log.d(TAG, "Sum: " + snapshot.get(AggregateField.sum("population"))); } else { Log.d(TAG, "Aggregation failed: ", task.getException()); } } });
Kotlin+KTX
Android
val query = db.collection("cities") val aggregateQuery = query.aggregate(AggregateField.sum("population")) aggregateQuery.get(AggregateSource.SERVER).addOnCompleteListener { task -> if (task.isSuccessful) { // Aggregate fetched successfully val snapshot = task.result Log.d(TAG, "Sum: ${snapshot.get(AggregateField.sum("population"))}") } else { Log.d(TAG, "Aggregate failed: ", task.getException()) } }
Java
collection = db.collection("cities"); snapshot = collection.aggregate(sum("population")).get().get(); System.out.println("Sum: " + snapshot.get(sum("population")));
Node.js
const coll = firestore.collection('cities'); const sumAggregateQuery = coll.aggregate({ totalPopulation: AggregateField.sum('population'), }); const snapshot = await sumAggregateQuery.get(); console.log('totalPopulation: ', snapshot.data().totalPopulation);
Python
collection_ref = client.collection("users") aggregate_query = aggregation.AggregationQuery(collection_ref) aggregate_query.sum("coins", alias="sum") results = aggregate_query.get() for result in results: print(f"Alias of results from query: {result[0].alias}") print(f"Sum of results from query: {result[0].value}")
Einfach loslegen (Go)
func createSumQuery(w io.Writer, projectID string) error { ctx := context.Background() client, err := firestore.NewClient(ctx, projectID) if err != nil { return err } defer client.Close() collection := client.Collection("users") query := collection.Where("born", ">", 1850) aggregationQuery := query.NewAggregationQuery().WithSum("coins", "sum_coins") results, err := aggregationQuery.Get(ctx) if err != nil { return err } sum, ok := results["sum_coins"] if !ok { return errors.New("firestore: couldn't get alias for SUM from results") } sumValue := sum.(*firestorepb.Value) fmt.Fprintf(w, "Sum of results from query: %d\n", sumValue.GetIntegerValue()) return nil }
Die Aggregation sum()
berücksichtigt alle Filter für die Abfrage und alle Begrenzungsklauseln. Beispiel:
Webversion 9
const coll = collection(firestore, 'cities'); const q = query(coll, where('capital', '==', true)); const snapshot = await getAggregateFromServer(q, { totalPopulation: sum('population') }); console.log('totalPopulation: ', snapshot.data().totalPopulation);
Swift
let query = db.collection("cities").whereField("capital", isEqualTo: true) let aggregateQuery = query.aggregate([AggregateField.sum("population")]) do { let snapshot = try await aggregateQuery.getAggregation(source: .server) print(snapshot.get(AggregateField.sum("population"))) } catch { print(error) }
Objective-C
FIRQuery *query = [[self.db collectionWithPath:@"cities"] queryWhereFilter:[FIRFilter filterWhereField:@"capital" isEqualTo:@YES]]; FIRAggregateQuery *aggregateQuery = [query aggregate:@[ [FIRAggregateField aggregateFieldForSumOfField:@"population"]]]; [aggregateQuery aggregationWithSource:FIRAggregateSourceServer completion:^(FIRAggregateQuerySnapshot *snapshot, NSError *error) { if (error != nil) { NSLog(@"Error fetching aggregate: %@", error); } else { NSLog(@"Sum: %@", [snapshot valueForAggregateField:[FIRAggregateField aggregateFieldForSumOfField:@"population"]]); } }];
Java
Android
Query query = db.collection("cities").whereEqualTo("capital", true); AggregateQuery aggregateQuery = query.aggregate(AggregateField.sum("population")); aggregateQuery.get(AggregateSource.SERVER).addOnCompleteListener(new OnCompleteListener<AggregateQuerySnapshot>() { @Override public void onComplete(@NonNull Task<AggregateQuerySnapshot> task) { if (task.isSuccessful()) { // Aggregate fetched successfully AggregateQuerySnapshot snapshot = task.getResult(); Log.d(TAG, "Sum: " + snapshot.get(AggregateField.sum("population"))); } else { Log.d(TAG, "Aggregation failed: ", task.getException()); } } });
Kotlin+KTX
Android
val query = db.collection("cities").whereEqualTo("capital", true) val aggregateQuery = query.aggregate(AggregateField.sum("population")) aggregateQuery.get(AggregateSource.SERVER).addOnCompleteListener { task -> if (task.isSuccessful) { // Aggregate fetched successfully val snapshot = task.result Log.d(TAG, "Sum: ${snapshot.get(AggregateField.sum("population"))}") } else { Log.d(TAG, "Aggregate failed: ", task.getException()) } }
Java
collection = db.collection("cities"); query = collection.whereEqualTo("state", "CA"); snapshot = query.aggregate(sum("population")).get().get(); System.out.println("Sum: " + snapshot.get(sum("population")));
Node.js
const coll = firestore.collection('cities'); const q = coll.where("capital", "==", true); const sumAggregateQuery = q.aggregate({ totalPopulation: AggregateField.sum('population'), }); const snapshot = await sumAggregateQuery.get(); console.log('totalPopulation: ', snapshot.data().totalPopulation);
Python
collection_ref = client.collection("users") query = collection_ref.where(filter=FieldFilter("people", "==", "Matthew")) aggregate_query = aggregation.AggregationQuery(query) aggregate_query.sum("coins", alias="sum") results = aggregate_query.get() for result in results: print(f"Alias of results from query: {result[0].alias}") print(f"Sum of results from query: {result[0].value}")
Einfach loslegen (Go)
func createSumQuery(w io.Writer, projectID string) error { ctx := context.Background() client, err := firestore.NewClient(ctx, projectID) if err != nil { return err } defer client.Close() collection := client.Collection("users") query := collection.Where("born", ">", 1850).Limit(5) aggregationQuery := query.NewAggregationQuery().WithSum("coins", "sum_coins") results, err := aggregationQuery.Get(ctx) if err != nil { return err } sum, ok := results["sum_coins"] if !ok { return errors.New("firestore: couldn't get alias for SUM from results") } sumValue := sum.(*firestorepb.Value) fmt.Fprintf(w, "Sum of results from query: %d\n", sumValue.GetIntegerValue()) return nil }
Aggregationsmethode average()
verwenden
Verwenden Sie die Aggregation average()
, um den Durchschnitt der numerischen Werte zurückzugeben, die einer bestimmten Abfrage entsprechen. Beispiel:
Webversion 9
const coll = collection(firestore, 'cities'); const snapshot = await getAggregateFromServer(coll, { averagePopulation: average('population') }); console.log('averagePopulation: ', snapshot.data().averagePopulation);
Swift
let query = db.collection("cities") let aggregateQuery = query.aggregate([AggregateField.average("population")]) do { let snapshot = try await aggregateQuery.getAggregation(source: .server) print(snapshot.get(AggregateField.average("population"))) } catch { print(error) }
Objective-C
FIRQuery *query = [self.db collectionWithPath:@"cities"]; FIRAggregateQuery *aggregateQuery = [query aggregate:@[ [FIRAggregateField aggregateFieldForAverageOfField:@"population"]]]; [aggregateQuery aggregationWithSource:FIRAggregateSourceServer completion:^(FIRAggregateQuerySnapshot *snapshot, NSError *error) { if (error != nil) { NSLog(@"Error fetching aggregate: %@", error); } else { NSLog(@"Avg: %@", [snapshot valueForAggregateField:[FIRAggregateField aggregateFieldForAverageOfField:@"population"]]); } }];
Java
Android
Query query = db.collection("cities"); AggregateQuery aggregateQuery = query.aggregate(AggregateField.average("population")); aggregateQuery.get(AggregateSource.SERVER).addOnCompleteListener(new OnCompleteListener<AggregateQuerySnapshot>() { @Override public void onComplete(@NonNull Task<AggregateQuerySnapshot> task) { if (task.isSuccessful()) { // Aggregate fetched successfully AggregateQuerySnapshot snapshot = task.getResult(); Log.d(TAG, "Average: " + snapshot.get(AggregateField.average("population"))); } else { Log.d(TAG, "Aggregation failed: ", task.getException()); } } });
Kotlin+KTX
Android
val query = db.collection("cities") val aggregateQuery = query.aggregate(AggregateField.average("population")) aggregateQuery.get(AggregateSource.SERVER).addOnCompleteListener { task -> if (task.isSuccessful) { // Aggregate fetched successfully val snapshot = task.result Log.d(TAG, "Average: ${snapshot.get(AggregateField.average("population"))}") } else { Log.d(TAG, "Aggregate failed: ", task.getException()) } }
Java
collection = db.collection("cities"); snapshot = collection.aggregate(average("population")).get().get(); System.out.println("Average: " + snapshot.get(average("population")));
Node.js
const coll = firestore.collection('cities'); const averageAggregateQuery = coll.aggregate({ averagePopulation: AggregateField.average('population'), }); const snapshot = await averageAggregateQuery.get(); console.log('averagePopulation: ', snapshot.data().averagePopulation);
Python
collection_ref = client.collection("users") aggregate_query = aggregation.AggregationQuery(collection_ref) aggregate_query.avg("coins", alias="avg") results = aggregate_query.get() for result in results: print(f"Alias of results from query: {result[0].alias}") print(f"Average of results from query: {result[0].value}")
Einfach loslegen (Go)
func createAvgQuery(w io.Writer, projectID string) error { ctx := context.Background() client, err := firestore.NewClient(ctx, projectID) if err != nil { return err } defer client.Close() collection := client.Collection("users") query := collection.Where("born", ">", 1850) aggregationQuery := query.NewAggregationQuery().WithAvg("coins", "avg_coins") results, err := aggregationQuery.Get(ctx) if err != nil { return err } avg, ok := results["avg_coins"] if !ok { return errors.New("firestore: couldn't get alias for AVG from results") } avgValue := avg.(*firestorepb.Value) fmt.Fprintf(w, "Avg of results from query: %d\n", avgValue.GetDoubleValue()) return nil }
Die Aggregation average()
berücksichtigt alle Filter in der Abfrage und alle Limitklauseln. Beispiel:
Webversion 9
const coll = collection(firestore, 'cities'); const q = query(coll, where('capital', '==', true)); const snapshot = await getAggregateFromServer(q, { averagePopulation: average('population') }); console.log('averagePopulation: ', snapshot.data().averagePopulation);
Swift
let query = db.collection("cities").whereField("capital", isEqualTo: true) let aggregateQuery = query.aggregate([AggregateField.average("population")]) do { let snapshot = try await aggregateQuery.getAggregation(source: .server) print(snapshot.get(AggregateField.average("population"))) } catch { print(error) }
Objective-C
FIRQuery *query = [[self.db collectionWithPath:@"cities"] queryWhereFilter:[FIRFilter filterWhereField:@"capital" isEqualTo:@YES]]; FIRAggregateQuery *aggregateQuery = [query aggregate:@[ [FIRAggregateField aggregateFieldForAverageOfField:@"population"]]]; [aggregateQuery aggregationWithSource:FIRAggregateSourceServer completion:^(FIRAggregateQuerySnapshot *snapshot, NSError *error) { if (error != nil) { NSLog(@"Error fetching aggregate: %@", error); } else { NSLog(@"Avg: %@", [snapshot valueForAggregateField:[FIRAggregateField aggregateFieldForAverageOfField:@"population"]]); } }];
Java
Android
Query query = db.collection("cities").whereEqualTo("capital", true); AggregateQuery aggregateQuery = query.aggregate(AggregateField.average("population")); aggregateQuery.get(AggregateSource.SERVER).addOnCompleteListener(new OnCompleteListener<AggregateQuerySnapshot>() { @Override public void onComplete(@NonNull Task<AggregateQuerySnapshot> task) { if (task.isSuccessful()) { // Aggregate fetched successfully AggregateQuerySnapshot snapshot = task.getResult(); Log.d(TAG, "Average: " + snapshot.get(AggregateField.average("population"))); } else { Log.d(TAG, "Aggregation failed: ", task.getException()); } } });
Kotlin+KTX
Android
val query = db.collection("cities").whereEqualTo("capital", true) val aggregateQuery = query.aggregate(AggregateField.average("population")) aggregateQuery.get(AggregateSource.SERVER).addOnCompleteListener { task -> if (task.isSuccessful) { // Aggregate fetched successfully val snapshot = task.result Log.d(TAG, "Average: ${snapshot.get(AggregateField.average("population"))}") } else { Log.d(TAG, "Aggregate failed: ", task.getException()) } }
Java
collection = db.collection("cities"); query = collection.whereEqualTo("state", "CA"); snapshot = query.aggregate(average("population")).get().get(); System.out.println("Average: " + snapshot.get(average("population")));
Node.js
const coll = firestore.collection('cities'); const q = coll.where("capital", "==", true); const averageAggregateQuery = q.aggregate({ averagePopulation: AggregateField.average('population'), }); const snapshot = await averageAggregateQuery.get(); console.log('averagePopulation: ', snapshot.data().averagePopulation);
Python
collection_ref = client.collection("users") query = collection_ref.where(filter=FieldFilter("people", "==", "Matthew")) aggregate_query = aggregation.AggregationQuery(query) aggregate_query.avg("coins", alias="avg") results = aggregate_query.get() for result in results: print(f"Alias of results from query: {result[0].alias}") print(f"Average of results from query: {result[0].value}")
Einfach loslegen (Go)
func createAvgQuery(w io.Writer, projectID string) error { ctx := context.Background() client, err := firestore.NewClient(ctx, projectID) if err != nil { return err } defer client.Close() collection := client.Collection("users") query := collection.Where("born", ">", 1850).Limit(5) aggregationQuery := query.NewAggregationQuery().WithAvg("coins", "avg_coins") results, err := aggregationQuery.Get(ctx) if err != nil { return err } avg, ok := results["avg_coins"] if !ok { return errors.New("firestore: couldn't get alias for AVG from results") } avgValue := avg.(*firestorepb.Value) fmt.Fprintf(w, "Avg of results from query: %d\n", avgValue.GetDoubleValue()) return nil }
Mehrere Aggregationen in einer Abfrage berechnen
Sie können mehrere Aggregationen in einer einzigen Aggregationspipeline kombinieren. Dadurch kann die Anzahl der erforderlichen Indexlesevorgänge reduziert werden. Wenn die Abfrage Aggregationen für mehrere Felder enthält, ist möglicherweise ein zusammengesetzter Index erforderlich. In diesem Fall schlägt Firestore einen Index vor.
Im folgenden Beispiel werden mehrere Aggregationen in einer einzigen Aggregationsabfrage ausgeführt:
Webversion 9
const coll = collection(firestore, 'cities'); const snapshot = await getAggregateFromServer(coll, { countOfDocs: count(), totalPopulation: sum('population'), averagePopulation: average('population') }); console.log('countOfDocs: ', snapshot.data().countOfDocs); console.log('totalPopulation: ', snapshot.data().totalPopulation); console.log('averagePopulation: ', snapshot.data().averagePopulation);
Swift
let query = db.collection("cities") let aggregateQuery = query.aggregate([ AggregateField.count(), AggregateField.sum("population"), AggregateField.average("population")]) do { let snapshot = try await aggregateQuery.getAggregation(source: .server) print("Count: \(snapshot.get(AggregateField.count()))") print("Sum: \(snapshot.get(AggregateField.sum("population")))") print("Average: \(snapshot.get(AggregateField.average("population")))") } catch { print(error) }
Objective-C
FIRQuery *query = [self.db collectionWithPath:@"cities"]; FIRAggregateQuery *aggregateQuery = [query aggregate:@[ [FIRAggregateField aggregateFieldForCount], [FIRAggregateField aggregateFieldForSumOfField:@"population"], [FIRAggregateField aggregateFieldForAverageOfField:@"population"]]]; [aggregateQuery aggregationWithSource:FIRAggregateSourceServer completion:^(FIRAggregateQuerySnapshot *snapshot, NSError *error) { if (error != nil) { NSLog(@"Error fetching aggregate: %@", error); } else { NSLog(@"Count: %@", [snapshot valueForAggregateField:[FIRAggregateField aggregateFieldForCount]]); NSLog(@"Sum: %@", [snapshot valueForAggregateField:[FIRAggregateField aggregateFieldForSumOfField:@"population"]]); NSLog(@"Avg: %@", [snapshot valueForAggregateField:[FIRAggregateField aggregateFieldForAverageOfField:@"population"]]); } }];
Java
Android
Query query = db.collection("cities"); AggregateQuery aggregateQuery = query.aggregate( AggregateField.count(), AggregateField.sum("population"), AggregateField.average("population")); aggregateQuery.get(AggregateSource.SERVER).addOnCompleteListener(new OnCompleteListener<AggregateQuerySnapshot>() { @Override public void onComplete(@NonNull Task<AggregateQuerySnapshot> task) { if (task.isSuccessful()) { // Aggregate fetched successfully AggregateQuerySnapshot snapshot = task.getResult(); Log.d(TAG, "Count: " + snapshot.get(AggregateField.count())); Log.d(TAG, "Sum: " + snapshot.get(AggregateField.sum("population"))); Log.d(TAG, "Average: " + snapshot.get(AggregateField.average("population"))); } else { Log.d(TAG, "Aggregation failed: ", task.getException()); } } });
Kotlin+KTX
Android
val query = db.collection("cities") val aggregateQuery = query.aggregate( AggregateField.count(), AggregateField.sum("population"), AggregateField.average("population") ) aggregateQuery.get(AggregateSource.SERVER).addOnCompleteListener { task -> if (task.isSuccessful) { // Aggregate fetched successfully val snapshot = task.result Log.d(TAG, "Count: ${snapshot.get(AggregateField.count())}") Log.d(TAG, "Sum: ${snapshot.get(AggregateField.sum("population"))}") Log.d(TAG, "Average: ${snapshot.get(AggregateField.average("population"))}") } else { Log.d(TAG, "Aggregate failed: ", task.getException()) } }
Java
collection = db.collection("cities"); query = collection.whereEqualTo("state", "CA"); AggregateQuery aggregateQuery = query.aggregate(count(), sum("population"), average("population")); snapshot = aggregateQuery.get().get(); System.out.println("Count: " + snapshot.getCount()); System.out.println("Sum: " + snapshot.get(sum("population"))); System.out.println("Average: " + snapshot.get(average("population")));
Node.js
const coll = firestore.collection('cities'); const aggregateQuery = coll.aggregate({ countOfDocs: AggregateField.count(), totalPopulation: AggregateField.sum('population'), averagePopulation: AggregateField.average('population') }); const snapshot = await aggregateQuery.get(); console.log('countOfDocs: ', snapshot.data().countOfDocs); console.log('totalPopulation: ', snapshot.data().totalPopulation); console.log('averagePopulation: ', snapshot.data().averagePopulation);
Python
collection_ref = client.collection("users") query = collection_ref.where(filter=FieldFilter("people", "==", "Matthew")) aggregate_query = aggregation.AggregationQuery(query) aggregate_query.sum("coins", alias="sum").avg("coins", alias="avg") results = aggregate_query.get() for result in results: print(f"Alias of results from query: {result[0].alias}") print(f"Aggregation of results from query: {result[0].value}")
Einfach loslegen (Go)
func createMultiAggregationQuery(w io.Writer, projectID string) error { ctx := context.Background() client, err := firestore.NewClient(ctx, projectID) if err != nil { return err } defer client.Close() collection := client.Collection("users") query := collection.Where("born", ">", 1850) aggregationQuery := query.NewAggregationQuery().WithCount("count").WithSum("coins", "sum_coins").WithAvg("coins", "avg_coins") results, err := aggregationQuery.Get(ctx) if err != nil { return err } }
Abfragen mit mehreren Aggregationen umfassen nur die Dokumente, die alle Felder in den einzelnen Aggregationen enthalten. Dies kann zu anderen Ergebnissen führen, wenn jede Aggregation separat ausgeführt wird.
Sicherheitsregeln für Aggregationsabfragen
Firestore-Sicherheitsregeln funktionieren bei Aggregationsabfragen genauso wie für Abfragen, die Dokumente zurückgeben. Mit anderen Worten: Wenn Ihre Regeln es Clients erlauben, bestimmte Sammlungs- oder Sammlungsgruppenabfragen auszuführen, können Clients auch die Aggregation dieser Abfragen durchführen. Weitere Informationen zur Interaktion von Firestore-Sicherheitsregeln mit Abfragen
Verhalten und Einschränkungen
Beachten Sie beim Arbeiten mit Aggregationsabfragen die folgenden Verhaltensweisen und Einschränkungen:
Aggregationsabfragen können nicht mit Echtzeit-Listenern und Offlineabfragen verwendet werden. Aggregationsabfragen werden nur über eine direkte Serverantwort unterstützt. Abfragen werden nur vom Firestore-Back-End verarbeitet, wobei der lokale Cache und alle gepufferten Updates übersprungen werden. Dieses Verhalten ist mit Vorgängen identisch, die innerhalb von Firestore-Transaktionen ausgeführt werden.
Wenn eine Aggregation innerhalb von 60 Sekunden nicht aufgelöst werden kann, wird der Fehler
DEADLINE_EXCEEDED
zurückgegeben. Die Leistung hängt von Ihrer Indexkonfiguration und der Größe des Datasets ab.Wenn der Vorgang nicht innerhalb der 60 Sekunden abgeschlossen werden kann, können Sie das Problem umgehen, indem Sie für große Datasets Zähler verwenden.
Aggregationsabfragen lesen aus Indexeinträgen und enthalten nur indexierte Felder.
Durch das Hinzufügen einer
OrderBy
-Klausel zu einer Aggregationsabfrage wird die Aggregation auf die Dokumente beschränkt, in denen sich das Sortierfeld befindet.Bei Aggregationen
sum()
undaverage()
werden nicht numerische Werte ignoriert.sum()
- undaverage()
-Aggregationen berücksichtigen nur ganzzahlige Werte und Gleitkommazahlenwerte.Wenn Sie mehrere Aggregationen in einer einzigen Abfrage kombinieren, ignorieren
sum()
undaverage()
nicht numerische Werte, währendcount()
nicht numerische Werte enthält.Wenn Sie Aggregationen kombinieren, die sich in verschiedenen Feldern befinden, umfasst die Berechnung nur die Dokumente, die alle diese Felder enthalten.
Preise
Die Preise für Aggregationsabfragen hängen von der Anzahl der Indexeinträge ab, die mit der Abfrage übereinstimmen. Für eine große Anzahl übereinstimmender Einträge wird Ihnen eine geringe Anzahl von Lesevorgängen in Rechnung gestellt.
Ausführliche Preisinformationen
Nächste Schritte
- Daten abfragen und filtern
- Lesevorgänge speichern, wenn nur Ergebnisse gezählt werden sollen