Google is committed to advancing racial equity for Black communities. See how.
Diese Seite wurde von der Cloud Translation API übersetzt.
Switch to English

Paginieren Sie Daten mit Abfragecursorn

Mit Abfragecursorn im Cloud Firestore können Sie die von einer Abfrage zurückgegebenen Daten gemäß den in Ihrer Abfrage definierten Parametern in Stapel aufteilen.

Abfragecursor definieren die Start- und Endpunkte für eine Abfrage, sodass Sie:

  • Gibt eine Teilmenge der Daten zurück.
  • Abfrageergebnisse paginieren.

Um jedoch einen bestimmten Bereich für eine Abfrage zu definieren, sollten Sie die in Simple Queries beschriebene where() -Methode verwenden.

Fügen Sie einer Abfrage einen einfachen Cursor hinzu

Verwenden Sie die startAt() oder startAfter() , um den Startpunkt für eine Abfrage zu definieren. Die Methode startAt() enthält den Startpunkt, während die Methode startAfter() ausschließt.

Wenn Sie beispielsweise startAt(A) in einer Abfrage verwenden, wird das gesamte Alphabet zurückgegeben. Wenn Sie stattdessen startAfter(A) verwenden, wird BZ .

Netz
citiesRef.orderBy("population").startAt(1000000)
Schnell
// Get all cities with population over one million, ordered by population.
db.collection("cities")
    .order(by: "population")
    .start(at: [1000000])
Ziel c
// Get all cities with population over one million, ordered by population.
[[[db collectionWithPath:@"cities"]
    queryOrderedByField:@"population"]
    queryStartingAtValues:@[ @1000000 ]];
  

Java

// Get all cities with a population >= 1,000,000, ordered by population,
db.collection("cities")
        .orderBy("population")
        .startAt(1000000);

Kotlin + KTX

// Get all cities with a population >= 1,000,000, ordered by population,
db.collection("cities")
        .orderBy("population")
        .startAt(1000000)
Java
Query query = cities.orderBy("population").startAt(4921000L);
Python
cities_ref = db.collection(u'cities')
query_start_at = cities_ref.order_by(u'population').start_at({
    u'population': 1000000
})
C ++
// Get all cities with a population >= 1,000,000, ordered by population,
db->Collection("cities")
    .OrderBy("population")
    .StartAt({FieldValue::Integer(1000000)});
  
Node.js
const startAtRes = await db.collection('cities')
  .orderBy('population')
  .startAt(1000000)
  .get();
Gehen
query := client.Collection("cities").OrderBy("population", firestore.Asc).StartAt(1000000)
PHP
$query = $citiesRef
    ->orderBy('population')
    ->startAt([1000000]);
Einheit
Query query = citiesRef.OrderBy("Population").StartAt(1000000);
C #
Query query = citiesRef.OrderBy("Population").StartAt(1000000);
Rubin
query = cities_ref.order("population").start_at(1_000_000)

Verwenden endAt() ähnlicher Weise die endAt() oder endBefore() , um einen Endpunkt für Ihre Abfrageergebnisse zu definieren.

Netz
citiesRef.orderBy("population").endAt(1000000)
Schnell
// Get all cities with population less than one million, ordered by population.
db.collection("cities")
    .order(by: "population")
    .end(at: [1000000])
Ziel c
// Get all cities with population less than one million, ordered by population.
[[[db collectionWithPath:@"cities"]
    queryOrderedByField:@"population"]
    queryEndingAtValues:@[ @1000000 ]];
  

Java

// Get all cities with a population <= 1,000,000, ordered by population,
db.collection("cities")
        .orderBy("population")
        .endAt(1000000);

Kotlin + KTX

// Get all cities with a population <= 1,000,000, ordered by population,
db.collection("cities")
        .orderBy("population")
        .endAt(1000000)
Java
Query query = cities.orderBy("population").endAt(4921000L);
Python
cities_ref = db.collection(u'cities')
query_end_at = cities_ref.order_by(u'population').end_at({
    u'population': 1000000
})
C ++
// Get all cities with a population <= 1,000,000, ordered by population,
db->Collection("cities")
    .OrderBy("population")
    .EndAt({FieldValue::Integer(1000000)});
  
Node.js
const endAtRes = await db.collection('cities')
  .orderBy('population')
  .endAt(1000000)
  .get();
Gehen
query := client.Collection("cities").OrderBy("population", firestore.Asc).EndAt(1000000)
PHP
$query = $citiesRef
    ->orderBy('population')
    ->endAt([1000000]);
Einheit
Query query = citiesRef.OrderBy("Population").EndAt(1000000);
C #
Query query = citiesRef.OrderBy("Population").EndAt(1000000);
Rubin
query = cities_ref.order("population").end_at(1_000_000)

Verwenden Sie einen Dokumentschnappschuss, um den Abfragecursor zu definieren

Sie können der Cursorklausel auch einen Dokumentschnappschuss als Start- oder Endpunkt des Abfragecursors übergeben. Die Werte im Dokumentschnappschuss dienen als Werte im Abfragecursor.

Machen Sie beispielsweise eine Momentaufnahme eines "San Francisco" -Dokuments in Ihrem Datensatz mit Städten und Bevölkerungsgruppen. Verwenden Sie dann diesen Dokumentschnappschuss als Startpunkt für Ihren Populationsabfragecursor. Ihre Abfrage gibt alle Städte mit einer Bevölkerung zurück, die größer oder gleich der von San Francisco ist, wie im Dokumentschnappschuss definiert.

Netz
var citiesRef = db.collection("cities");

return citiesRef.doc("SF").get().then(function(doc) {
    // Get all cities with a population bigger than San Francisco
    var biggerThanSf = citiesRef
        .orderBy("population")
        .startAt(doc);

    // ...
});
Schnell
db.collection("cities")
    .document("SF")
    .addSnapshotListener { (document, error) in
        guard let document = document else {
            print("Error retreving cities: \(error.debugDescription)")
            return
        }

        // Get all cities with a population greater than or equal to San Francisco.
        let sfSizeOrBigger = db.collection("cities")
            .order(by: "population")
            .start(atDocument: document)
}
Ziel c
[[[db collectionWithPath:@"cities"] documentWithPath:@"SF"]
    addSnapshotListener:^(FIRDocumentSnapshot *snapshot, NSError *error) {
      if (snapshot == nil) {
        NSLog(@"Error retreiving cities: %@", error);
        return;
      }
      // Get all cities with a population greater than or equal to San Francisco.
      FIRQuery *sfSizeOrBigger = [[[db collectionWithPath:@"cities"]
          queryOrderedByField:@"population"]
          queryStartingAtDocument:snapshot];
    }];
  

Java

// Get the data for "San Francisco"
db.collection("cities").document("SF")
        .get()
        .addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
            @Override
            public void onSuccess(DocumentSnapshot documentSnapshot) {
                // Get all cities with a population bigger than San Francisco.
                Query biggerThanSf = db.collection("cities")
                        .orderBy("population")
                        .startAt(documentSnapshot);

                // ...
            }
        });

Kotlin + KTX

// Get the data for "San Francisco"
db.collection("cities").document("SF")
        .get()
        .addOnSuccessListener { documentSnapshot ->
            // Get all cities with a population bigger than San Francisco.
            val biggerThanSf = db.collection("cities")
                    .orderBy("population")
                    .startAt(documentSnapshot)

            // ...
        }
Java
// Fetch the snapshot with an API call, waiting for a maximum of 30 seconds for a result.
ApiFuture<DocumentSnapshot> future = db.collection("cities").document("SF").get();
DocumentSnapshot snapshot = future.get(30, TimeUnit.SECONDS);

// Construct the query
Query query = db.collection("cities").orderBy("population").startAt(snapshot);
Python
doc_ref = db.collection(u'cities').document(u'SF')

snapshot = doc_ref.get()
start_at_snapshot = db.collection(
    u'cities').order_by(u'population').start_at(snapshot)
C ++
db->Collection("cities").Document("SF").Get().OnCompletion(
    [db](const Future<DocumentSnapshot>& future) {
      if (future.error() == Error::kErrorOk) {
        const DocumentSnapshot& document_snapshot = *future.result();
        Query bigger_than_sf = db->Collection("cities")
                                   .OrderBy("population")
                                   .StartAt({document_snapshot});
        // ...
      }
    });
  
Node.js
const docRef = db.collection('cities').doc('SF');
const snapshot = await docRef.get();
const startAtSnapshot = db.collection('cities')
  .orderBy('population')
  .startAt(snapshot);

await startAtSnapshot.limit(10).get();
Gehen
cities := client.Collection("cities")
dsnap, err := cities.Doc("SF").Get(ctx)
if err != nil {
	fmt.Println(err)
}
query := cities.OrderBy("population", firestore.Asc).StartAt(dsnap.Data()["population"]).Documents(ctx)
PHP
$citiesRef = $db->collection('cities');
$docRef = $citiesRef->document('SF');
$snapshot = $docRef->snapshot();

$query = $citiesRef
    ->orderBy('population')
    ->startAt($snapshot);
Einheit
CollectionReference citiesRef = db.Collection("cities");
DocumentReference docRef = citiesRef.Document("SF");
docRef.GetSnapshotAsync().ContinueWith((snapshotTask) =>
{
    Query query = citiesRef.OrderBy("Population").StartAt(snapshotTask.Result);
});
C #
CollectionReference citiesRef = db.Collection("cities");
DocumentReference docRef = citiesRef.Document("SF");
DocumentSnapshot snapshot = await docRef.GetSnapshotAsync();
Query query = citiesRef.OrderBy("Population").StartAt(snapshot);
Rubin
// Snippet not available

Paginieren Sie eine Abfrage

Paginieren Sie Abfragen, indem Sie Abfragecursor mit der Methode limit() kombinieren. Verwenden Sie beispielsweise das letzte Dokument in einem Stapel als Start eines Cursors für den nächsten Stapel.

Netz
var first = db.collection("cities")
        .orderBy("population")
        .limit(25);

return first.get().then(function (documentSnapshots) {
  // Get the last visible document
  var lastVisible = documentSnapshots.docs[documentSnapshots.docs.length-1];
  console.log("last", lastVisible);

  // Construct a new query starting at this document,
  // get the next 25 cities.
  var next = db.collection("cities")
          .orderBy("population")
          .startAfter(lastVisible)
          .limit(25);
});
Schnell
// Construct query for first 25 cities, ordered by population
let first = db.collection("cities")
    .order(by: "population")
    .limit(to: 25)

first.addSnapshotListener { (snapshot, error) in
    guard let snapshot = snapshot else {
        print("Error retreving cities: \(error.debugDescription)")
        return
    }

    guard let lastSnapshot = snapshot.documents.last else {
        // The collection is empty.
        return
    }

    // Construct a new query starting after this document,
    // retrieving the next 25 cities.
    let next = db.collection("cities")
        .order(by: "population")
        .start(afterDocument: lastSnapshot)

    // Use the query for pagination.
    // ...
}
Ziel c
FIRQuery *first = [[[db collectionWithPath:@"cities"]
    queryOrderedByField:@"population"]
    queryLimitedTo:25];
[first addSnapshotListener:^(FIRQuerySnapshot *snapshot, NSError *error) {
  if (snapshot == nil) {
    NSLog(@"Error retreiving cities: %@", error);
    return;
  }
  if (snapshot.documents.count == 0) { return; }
  FIRDocumentSnapshot *lastSnapshot = snapshot.documents.lastObject;

  // Construct a new query starting after this document,
  // retreiving the next 25 cities.
  FIRQuery *next = [[[db collectionWithPath:@"cities"]
      queryOrderedByField:@"population"]
      queryStartingAfterDocument:lastSnapshot];
  // Use the query for pagination.
  // ...
}];
  

Java

// Construct query for first 25 cities, ordered by population
Query first = db.collection("cities")
        .orderBy("population")
        .limit(25);

first.get()
    .addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
        @Override
        public void onSuccess(QuerySnapshot documentSnapshots) {
            // ...

            // Get the last visible document
            DocumentSnapshot lastVisible = documentSnapshots.getDocuments()
                    .get(documentSnapshots.size() -1);

            // Construct a new query starting at this document,
            // get the next 25 cities.
            Query next = db.collection("cities")
                    .orderBy("population")
                    .startAfter(lastVisible)
                    .limit(25);

            // Use the query for pagination
            // ...
        }
    });

Kotlin + KTX

// Construct query for first 25 cities, ordered by population
val first = db.collection("cities")
        .orderBy("population")
        .limit(25)

first.get()
        .addOnSuccessListener { documentSnapshots ->
            // ...

            // Get the last visible document
            val lastVisible = documentSnapshots.documents[documentSnapshots.size() - 1]

            // Construct a new query starting at this document,
            // get the next 25 cities.
            val next = db.collection("cities")
                    .orderBy("population")
                    .startAfter(lastVisible)
                    .limit(25)

            // Use the query for pagination
            // ...
        }
Java
// Construct query for first 25 cities, ordered by population.
CollectionReference cities = db.collection("cities");
Query firstPage = cities.orderBy("population").limit(25);

// Wait for the results of the API call, waiting for a maximum of 30 seconds for a result.
ApiFuture<QuerySnapshot> future = firstPage.get();
List<QueryDocumentSnapshot> docs = future.get(30, TimeUnit.SECONDS).getDocuments();

// Construct query for the next 25 cities.
QueryDocumentSnapshot lastDoc = docs.get(docs.size() - 1);
Query secondPage = cities.orderBy("population").startAfter(lastDoc).limit(25);

future = secondPage.get();
docs = future.get(30, TimeUnit.SECONDS).getDocuments();
Python
cities_ref = db.collection(u'cities')
first_query = cities_ref.order_by(u'population').limit(3)

# Get the last document from the results
docs = first_query.stream()
last_doc = list(docs)[-1]

# Construct a new query starting at this document
# Note: this will not have the desired effect if
# multiple cities have the exact same population value
last_pop = last_doc.to_dict()[u'population']

next_query = (
    cities_ref
    .order_by(u'population')
    .start_after({
        u'population': last_pop
    })
    .limit(3)
)
# Use the query for pagination
# ...
C ++
// Construct query for first 25 cities, ordered by population
Query first = db->Collection("cities").OrderBy("population").Limit(25);

first.Get().OnCompletion([db](const Future<QuerySnapshot>& future) {
  if (future.error() != Error::kErrorOk) {
    // Handle error...
    return;
  }

  // Get the last visible document
  const QuerySnapshot& document_snapshots = *future.result();
  std::vector<DocumentSnapshot> documents = document_snapshots.documents();
  const DocumentSnapshot& last_visible = documents.back();

  // Construct a new query starting at this document,
  // get the next 25 cities.
  Query next = db->Collection("cities")
                   .OrderBy("population")
                   .StartAfter(last_visible)
                   .Limit(25);

  // Use the query for pagination
  // ...
});
  
Node.js
const first = db.collection('cities')
  .orderBy('population')
  .limit(3);

const snapshot = await first.get();

// Get the last document
const last = snapshot.docs[snapshot.docs.length - 1];

// Construct a new query starting at this document.
// Note: this will not have the desired effect if multiple
// cities have the exact same population value.
const next = db.collection('cities')
  .orderBy('population')
  .startAfter(last.data().population)
  .limit(3);

// Use the query for pagination
// ...
Gehen
cities := client.Collection("cities")

// Get the first 25 cities, ordered by population.
firstPage := cities.OrderBy("population", firestore.Asc).Limit(25).Documents(ctx)
docs, err := firstPage.GetAll()
if err != nil {
	return err
}

// Get the last document.
lastDoc := docs[len(docs)-1]

// Construct a new query to get the next 25 cities.
secondPage := cities.OrderBy("population", firestore.Asc).
	StartAfter(lastDoc.Data()["population"]).
	Limit(25)

// ...
PHP
$citiesRef = $db->collection('cities');
$firstQuery = $citiesRef->orderBy('population')->limit(3);

# Get the last document from the results
$documents = $firstQuery->documents();
$lastPopulation = 0;
foreach ($documents as $document) {
    $lastPopulation = $document['population'];
}

# Construct a new query starting at this document
# Note: this will not have the desired effect if multiple cities have the exact same population value
$nextQuery = $citiesRef->orderBy('population')->startAfter([$lastPopulation]);
$snapshot = $nextQuery->documents();
Einheit
CollectionReference citiesRef = db.Collection("cities");
Query firstQuery = citiesRef.OrderBy("Population").Limit(3);

// Get the last document from the results
firstQuery.GetSnapshotAsync().ContinueWith((querySnapshotTask) =>
{
    long lastPopulation = 0;
    foreach (DocumentSnapshot documentSnapshot in querySnapshotTask.Result.Documents)
    {
        lastPopulation = documentSnapshot.GetValue<long>("Population");
    }

    // Construct a new query starting at this document.
    // Note: this will not have the desired effect if multiple cities have the exact same population value
    Query secondQuery = citiesRef.OrderBy("Population").StartAfter(lastPopulation);
    Task<QuerySnapshot> secondQuerySnapshot = secondQuery.GetSnapshotAsync();
C #
CollectionReference citiesRef = db.Collection("cities");
Query firstQuery = citiesRef.OrderBy("Population").Limit(3);

// Get the last document from the results
QuerySnapshot querySnapshot = await firstQuery.GetSnapshotAsync();
long lastPopulation = 0;
foreach (DocumentSnapshot documentSnapshot in querySnapshot.Documents)
{
    lastPopulation = documentSnapshot.GetValue<long>("Population");
}

// Construct a new query starting at this document.
// Note: this will not have the desired effect if multiple cities have the exact same population value
Query secondQuery = citiesRef.OrderBy("Population").StartAfter(lastPopulation);
QuerySnapshot secondQuerySnapshot = await secondQuery.GetSnapshotAsync();
Rubin
cities_ref  = firestore.col collection_path
first_query = cities_ref.order("population").limit(3)

# Get the last document from the results.
last_population = 0
first_query.get do |city|
  last_population = city.data[:population]
end

# Construct a new query starting at this document.
# Note: this will not have the desired effect if multiple cities have the exact same population value.
second_query = cities_ref.order("population").start_after(last_population)
second_query.get do |city|
  puts "Document #{city.document_id} returned by paginated query cursor."
end

Stellen Sie den Cursor basierend auf mehreren Feldern ein

Wenn Sie einen Cursor verwenden, der auf einem Feldwert basiert (kein DocumentSnapshot), können Sie die Cursorposition präziser gestalten, indem Sie zusätzliche Felder hinzufügen. Dies ist besonders nützlich, wenn Ihr Datensatz mehrere Dokumente enthält, die alle denselben Wert für Ihr Cursorfeld haben, wodurch die Position des Cursors mehrdeutig wird. Sie können Ihrem Cursor zusätzliche Feldwerte hinzufügen, um den Start- oder Endpunkt weiter anzugeben und Mehrdeutigkeiten zu reduzieren.

In einem Datensatz, der alle Städte mit dem Namen "Springfield" in den USA enthält, gibt es beispielsweise mehrere Startpunkte für einen Abfragesatz, der bei "Springfield" beginnt:

Städte
Name Zustand
Springfield Massachusetts
Springfield Missouri
Springfield Wisconsin

Um an einem bestimmten Springfield zu beginnen, können Sie den Status als sekundäre Bedingung in Ihre Cursor-Klausel aufnehmen.

Netz
// Will return all Springfields
db.collection("cities")
   .orderBy("name")
   .orderBy("state")
   .startAt("Springfield")

// Will return "Springfield, Missouri" and "Springfield, Wisconsin"
db.collection("cities")
   .orderBy("name")
   .orderBy("state")
   .startAt("Springfield", "Missouri")
Schnell
// Will return all Springfields
db.collection("cities")
    .order(by: "name")
    .order(by: "state")
    .start(at: ["Springfield"])

// Will return "Springfield, Missouri" and "Springfield, Wisconsin"
db.collection("cities")
    .order(by: "name")
    .order(by: "state")
    .start(at: ["Springfield", "Missouri"])
Ziel c
// Will return all Springfields
[[[[db collectionWithPath:@"cities"]
    queryOrderedByField:@"name"]
    queryOrderedByField:@"state"]
    queryStartingAtValues:@[ @"Springfield" ]];
// Will return "Springfield, Missouri" and "Springfield, Wisconsin"
[[[[db collectionWithPath:@"cities"]
   queryOrderedByField:@"name"]
   queryOrderedByField:@"state"]
   queryStartingAtValues:@[ @"Springfield", @"Missouri" ]];
  

Java

// Will return all Springfields
db.collection("cities")
        .orderBy("name")
        .orderBy("state")
        .startAt("Springfield");

// Will return "Springfield, Missouri" and "Springfield, Wisconsin"
db.collection("cities")
        .orderBy("name")
        .orderBy("state")
        .startAt("Springfield", "Missouri");

Kotlin + KTX

// Will return all Springfields
db.collection("cities")
        .orderBy("name")
        .orderBy("state")
        .startAt("Springfield")

// Will return "Springfield, Missouri" and "Springfield, Wisconsin"
db.collection("cities")
        .orderBy("name")
        .orderBy("state")
        .startAt("Springfield", "Missouri")
Java
// Will return all Springfields
Query query1 = db.collection("cities").orderBy("name").orderBy("state").startAt("Springfield");

// Will return "Springfield, Missouri" and "Springfield, Wisconsin"
Query query2 =
    db.collection("cities").orderBy("name").orderBy("state").startAt("Springfield", "Missouri");
Python
start_at_name = (
    db.collection(u'cities')
    .order_by(u'name')
    .order_by(u'state')
    .start_at({
        u'name': u'Springfield'
    })
)

start_at_name_and_state = (
    db.collection(u'cities')
    .order_by(u'name')
    .order_by(u'state')
    .start_at({
        u'name': u'Springfield',
        u'state': u'Missouri'
    })
)
C ++
// This is not yet supported.
Node.js
// Will return all Springfields
const startAtNameRes = await db.collection('cities')
  .orderBy('name')
  .orderBy('state')
  .startAt('Springfield')
  .get();
// Will return 'Springfield, Missouri' and 'Springfield, Wisconsin'
const startAtNameAndStateRes = await db.collection('cities')
  .orderBy('name')
  .orderBy('state')
  .startAt('Springfield', 'Missouri')
  .get();
Gehen
// Will return all Springfields.
client.Collection("cities").
	OrderBy("name", firestore.Asc).
	OrderBy("state", firestore.Asc).
	StartAt("Springfield")

// Will return Springfields where state comes after Wisconsin.
client.Collection("cities").
	OrderBy("name", firestore.Asc).
	OrderBy("state", firestore.Asc).
	StartAt("Springfield", "Wisconsin")
PHP
// Will return all Springfields
$query1 = $db
    ->collection('cities')
    ->orderBy('name')
    ->orderBy('state')
    ->startAt(['Springfield']);

// Will return "Springfield, Missouri" and "Springfield, Wisconsin"
$query2 = $db
    ->collection('cities')
    ->orderBy('name')
    ->orderBy('state')
    ->startAt(['Springfield', 'Missouri']);
Einheit
Query query1 = db.Collection("cities").OrderBy("Name").OrderBy("State").StartAt("Springfield");
Query query2 = db.Collection("cities").OrderBy("Name").OrderBy("State").StartAt("Springfield", "Missouri");
C #
Query query1 = db.Collection("cities").OrderBy("Name").OrderBy("State").StartAt("Springfield");
Query query2 = db.Collection("cities").OrderBy("Name").OrderBy("State").StartAt("Springfield", "Missouri");
Rubin
# Will return all Springfields
query1 = firestore.col(collection_path).order("name").order("state").start_at("Springfield")

# Will return "Springfield, Missouri" and "Springfield, Wisconsin"
query2 = firestore.col(collection_path).order("name").order("state").start_at(["Springfield", "Missouri"])