يعالج استعلام التجميع البيانات من إدخالات متعددة للفهرس لإرجاع قيمة ملخص واحدة.
تدعم Cloud Firestore استعلامات التجميع التالية:
count()
sum()
average()
تحسب Cloud Firestore التجميع وينقل النتيجة فقط إلى تطبيقك. ومقارنةً بتنفيذ طلب بحث كامل وحساب التجميع في تطبيقك، تحفظ استعلامات التجميع في كل من عمليات قراءة المستندات التي يتم إصدار فواتيرها ووحدات البايت المنقولة.
تعتمد طلبات التجميع على إعدادات الفهرس الحالية التي تستخدمها استعلاماتك حاليًا، ويتم قياسها بشكل متناسب مع عدد إدخالات الفهرس التي يتم فحصها. يزداد وقت الاستجابة مع زيادة عدد العناصر في التجميع.
استخدام تجميع count()
يتيح لك استعلام تجميع count()
تحديد عدد المستندات في مجموعة أو طلب بحث.
يُرجى الرجوع إلى مثال البيانات التي أعددناها في قسم الحصول على البيانات.
تعرض عملية تجميع count()
التالية إجمالي عدد المدن في مجموعة cities
.
Web
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
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
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"), );
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
يراعي تجميع count()
أي فلاتر في طلب البحث وأي عبارات limit
.
Web
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
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
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"), );
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
استخدام تجميع sum()
استخدِم تجميع sum()
لعرض المجموع الإجمالي للقيم الرقمية التي تتطابق مع طلب بحث معيّن، على سبيل المثال:
Web
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
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
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}")
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 }
يأخذ تجميع sum()
في الاعتبار أي فلاتر على طلب البحث وأي عبارات محددة، على سبيل المثال:
Web
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
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
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}")
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 }
استخدام تجميع average()
استخدِم تجميع average()
لعرض متوسط القيم الرقمية التي تتطابق مع طلب بحث معيّن، على سبيل المثال:
Web
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
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
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}")
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 }
يأخذ تجميع average()
في الاعتبار أي فلاتر على طلب البحث وأي بنود
للحد، على سبيل المثال:
Web
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
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
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}")
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 }
حساب التجميعات المتعددة في طلب بحث
ويمكنك دمج تجميعات متعددة في مسار تجميع واحد. ويمكن أن يؤدي ذلك إلى تقليل عدد قراءات الفهرس المطلوبة. إذا كان الاستعلام يتضمن تجميعات في حقول متعددة، فقد يتطلب الاستعلام فهرسًا مركبًا. في هذه الحالة، يقترح Cloud Firestore فهرسًا.
يُجري المثال التالي عمليات تجميع متعددة في استعلام تجميع واحد:
Web
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
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
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}")
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 } }
تتضمن الاستعلامات ذات التجميعات المتعددة فقط المستندات التي تحتوي على جميع الحقول في كل تجميع. قد يؤدي ذلك إلى نتائج مختلفة من إجراء كل تجميع على حدة.
قواعد الأمان لطلبات التجميع
تعمل "قواعد أمان Cloud Firestore" على النحو نفسه في استعلامات التجميع التي تتّبعها الاستعلامات التي تعرض المستندات. بمعنى آخر، إذا كانت القواعد تسمح للعملاء بتنفيذ طلبات بحث معيّنة لمجموعة أو مجموعة، يمكن للعملاء أيضًا تنفيذ التجميع على طلبات البحث هذه. تعرَّف على مزيد من المعلومات عن كيفية تفاعل "قواعد أمان Cloud Firestore" مع طلبات البحث.
السلوك والقيود
أثناء التعامل مع استعلامات التجميع، لاحظ السلوك والقيود التالية:
لا يمكنك استخدام استعلامات التجميع مع مستمعين في الوقت الفعلي وطلبات البحث بلا اتصال بالإنترنت. لا يتم دعم استعلامات التجميع إلا من خلال الاستجابة المباشرة للخادم. لا يتم عرض طلبات البحث إلا من خلال خلفية Cloud Firestore، مع تخطي ذاكرة التخزين المؤقت المحلية وأي تحديثات مخزّنة مؤقتًا. وهذا السلوك مطابق للعمليات التي يتم تنفيذها داخل معاملات Cloud Firestore.
وإذا تعذَّر التعامل بشكل نهائي مع إحدى هذه المجموعات في غضون 60 ثانية، سيتم عرض الخطأ
DEADLINE_EXCEEDED
. ويعتمد الأداء على تهيئة الفهرس وعلى حجم مجموعة البيانات.إذا تعذّر إكمال العملية في غضون 60 ثانية، يمكن استخدام العدّادات مع مجموعات البيانات الكبيرة كحلّ بديل.
تتم قراءة استعلامات التجميع من إدخالات الفهرس، ولا تتضمن سوى الحقول المفهرسة.
تؤدي إضافة عبارة
OrderBy
إلى استعلام تجميع إلى تقييد التجميع إلى المستندات التي يوجد بها حقل الفرز.بالنسبة إلى تجميعات
sum()
وaverage()
، يتم تجاهل القيم غير الرقمية. ولا تأخذ مجموعاتsum()
وaverage()
في الاعتبار سوى قيم الأعداد الصحيحة وقيم أرقام النقاط العائمة.عند الجمع بين تجميعات متعدّدة في طلب بحث واحد، يُرجى العلم أنّ
sum()
وaverage()
يتجاهلان القيم غير الرقمية في حين أنّcount()
يتضمن قيمًا غير رقمية.في حال دمج التجميعات الموجودة في حقول مختلفة، ستتضمّن العملية الحسابية المستندات التي تحتوي على جميع هذه الحقول فقط.
الأسعار
يعتمد تسعير طلبات التجميع على عدد إدخالات الفهرس المطابقة للاستعلام. يتم تحصيل رسوم منك مقابل عدد صغير من القراءات لعدد كبير من الإدخالات المتطابقة.
يمكنك الاطّلاع على معلومات أكثر تفصيلاً.