Avec les curseurs de requête dans Cloud Firestore, vous pouvez diviser les données renvoyées par une requête en lots en fonction des paramètres que vous définissez dans votre requête.
Les curseurs de requêtes définissent les points de départ et d'arrêt d'une requête, ce qui vous permet de :
- renvoyer un sous-ensemble de données ;
- paginer les résultats des requêtes.
Toutefois, pour définir une plage spécifique pour une requête, vous devez utiliser la méthode where()
décrite dans la section Requêtes simples.
Ajouter un curseur simple à une requête
Utilisez les méthodes startAt()
ou startAfter()
pour définir le point de départ d'une requête.
La méthode startAt()
inclut le point de départ, tandis que la méthode startAfter()
l'exclut.
Par exemple, si vous utilisez la méthode startAt(A)
dans une requête, elle renvoie l'intégralité de l'alphabet.
En revanche, si vous utilisez startAfter(A)
, elle renvoie B-Z
.
Web
import { query, orderBy, startAt } from "firebase/firestore"; const q = query(citiesRef, orderBy("population"), startAt(1000000));
Web
citiesRef.orderBy("population").startAt(1000000);
Swift
// Get all cities with population over one million, ordered by population. db.collection("cities") .order(by: "population") .start(at: [1000000])
Objective-C
// Get all cities with population over one million, ordered by population. [[[db collectionWithPath:@"cities"] queryOrderedByField:@"population"] queryStartingAtValues:@[ @1000000 ]];
Kotlin+KTX
// Get all cities with a population >= 1,000,000, ordered by population, db.collection("cities") .orderBy("population") .startAt(1000000)
Java
// Get all cities with a population >= 1,000,000, ordered by population, db.collection("cities") .orderBy("population") .startAt(1000000);
Dart
db.collection("cities").orderBy("population").startAt([1000000]);
Java
Python
Python
C++
// Get all cities with a population >= 1,000,000, ordered by population, db->Collection("cities") .OrderBy("population") .StartAt({FieldValue::Integer(1000000)});
Node.js
Go
PHP
PHP
Pour en savoir plus sur l'installation et la création d'un client Cloud Firestore, consultez la page Bibliothèques clientes Cloud Firestore.
Unity
Query query = citiesRef.OrderBy("Population").StartAt(1000000);
C#
Ruby
De même, utilisez les méthodes endAt()
ou endBefore()
pour définir un point d'arrêt pour les résultats de votre requête.
Web
import { query, orderBy, endAt } from "firebase/firestore"; const q = query(citiesRef, orderBy("population"), endAt(1000000));
Web
citiesRef.orderBy("population").endAt(1000000);
Swift
// Get all cities with population less than one million, ordered by population. db.collection("cities") .order(by: "population") .end(at: [1000000])
Objective-C
// Get all cities with population less than one million, ordered by population. [[[db collectionWithPath:@"cities"] queryOrderedByField:@"population"] queryEndingAtValues:@[ @1000000 ]];
Kotlin+KTX
// Get all cities with a population <= 1,000,000, ordered by population, db.collection("cities") .orderBy("population") .endAt(1000000)
Java
// Get all cities with a population <= 1,000,000, ordered by population, db.collection("cities") .orderBy("population") .endAt(1000000);
Dart
db.collection("cities").orderBy("population").endAt([1000000]);
Java
Python
Python
C++
// Get all cities with a population <= 1,000,000, ordered by population, db->Collection("cities") .OrderBy("population") .EndAt({FieldValue::Integer(1000000)});
Node.js
Go
PHP
PHP
Pour en savoir plus sur l'installation et la création d'un client Cloud Firestore, consultez la page Bibliothèques clientes Cloud Firestore.
Unity
Query query = citiesRef.OrderBy("Population").EndAt(1000000);
C#
Ruby
Utiliser un instantané de document pour définir le curseur de la requête
Vous pouvez également transmettre l'instantané d'un document à la clause curseur en tant que point de départ ou d'arrêt du curseur de la requête. Les valeurs de l'instantané du document sont utilisées comme valeurs dans le curseur de la requête.
Par exemple, prenez un instantané d'un document "San Francisco" dans votre ensemble de données de villes et de populations. Ensuite, utilisez cet instantané du document comme point de départ de votre curseur de requête de population. Votre requête renvoie toutes les villes dont la population est supérieure ou égale à celle de San Francisco, telle que définie dans l'instantané du document.
Web
import { collection, doc, getDoc, query, orderBy, startAt } from "firebase/firestore"; const citiesRef = collection(db, "cities"); const docSnap = await getDoc(doc(citiesRef, "SF")); // Get all cities with a population bigger than San Francisco const biggerThanSf = query(citiesRef, orderBy("population"), startAt(docSnap)); // ...
Web
var citiesRef = db.collection("cities"); return citiesRef.doc("SF").get().then((doc) => { // Get all cities with a population bigger than San Francisco var biggerThanSf = citiesRef .orderBy("population") .startAt(doc); // ... });
Swift
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) }
Objective-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]; }];
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
// 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); // ... } });
Dart
db.collection("cities").doc("SF").get().then( (documentSnapshot) { final biggerThanSf = db .collection("cities") .orderBy("population") .startAtDocument(documentSnapshot); }, onError: (e) => print("Error: $e"), );
Java
Python
Python
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
Go
PHP
PHP
Pour en savoir plus sur l'installation et la création d'un client Cloud Firestore, consultez la page Bibliothèques clientes Cloud Firestore.
Unity
CollectionReference citiesRef = db.Collection("cities"); DocumentReference docRef = citiesRef.Document("SF"); docRef.GetSnapshotAsync().ContinueWith((snapshotTask) => { Query query = citiesRef.OrderBy("Population").StartAt(snapshotTask.Result); });
C#
Ruby
Paginer une requête
Pour paginer les requêtes, combinez les curseurs de requête avec la méthode limit()
.
Par exemple, utilisez le dernier document d'un lot comme début d'un curseur pour le lot suivant.
Web
import { collection, query, orderBy, startAfter, limit, getDocs } from "firebase/firestore"; // Query the first page of docs const first = query(collection(db, "cities"), orderBy("population"), limit(25)); const documentSnapshots = await getDocs(first); // Get the last visible document const lastVisible = documentSnapshots.docs[documentSnapshots.docs.length-1]; console.log("last", lastVisible); // Construct a new query starting at this document, // get the next 25 cities. const next = query(collection(db, "cities"), orderBy("population"), startAfter(lastVisible), limit(25));
Web
var first = db.collection("cities") .orderBy("population") .limit(25); return first.get().then((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); });
Swift
// 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. // ... }
Objective-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. // ... }];
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 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 // ... } });
Dart
// Construct query for first 25 cities, ordered by population final first = db.collection("cities").orderBy("population").limit(25); first.get().then( (documentSnapshots) { // Get the last visible document final lastVisible = documentSnapshots.docs[documentSnapshots.size - 1]; // Construct a new query starting at this document, // get the next 25 cities. final next = db .collection("cities") .orderBy("population") .startAfterDocument(lastVisible) .limit(25); // Use the query for pagination // ... }, onError: (e) => print("Error completing: $e"), );
Java
Python
Python
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
Go
PHP
PHP
Pour en savoir plus sur l'installation et la création d'un client Cloud Firestore, consultez la page Bibliothèques clientes Cloud Firestore.
Unity
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#
Ruby
Définir le curseur en fonction de plusieurs champs
Lorsque vous utilisez un curseur basé sur une valeur de champ, et non sur un instantané de document, vous pouvez préciser la position du curseur en ajoutant des champs supplémentaires. Cela est particulièrement utile si votre ensemble de données comprend plusieurs documents qui ont tous la même valeur pour votre champ de curseur, ce qui rend la position du curseur ambiguë. Vous pouvez ajouter des valeurs de champ supplémentaires à votre curseur pour spécifier le point de départ ou d'arrêt et réduire l'ambiguïté.
Par exemple, dans un ensemble de données contenant toutes les villes nommées "Springfield" aux États-Unis, il existe plusieurs points de départ pour une requête commençant à "Springfield" :
Villes | |
---|---|
Nom | État |
Springfield | Massachusetts |
Springfield | Missouri |
Springfield | Wisconsin |
Pour commencer à un champ Springfield spécifique, vous pouvez ajouter l'état en tant que condition secondaire dans votre clause curseur.
Web
// Will return all Springfields import { collection, query, orderBy, startAt } from "firebase/firestore"; const q1 = query(collection(db, "cities"), orderBy("name"), orderBy("state"), startAt("Springfield")); // Will return "Springfield, Missouri" and "Springfield, Wisconsin" const q2 = query(collection(db, "cities"), orderBy("name"), orderBy("state"), startAt("Springfield", "Missouri"));
Web
// 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");
Swift
// 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"])
Objective-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" ]];
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 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");
Dart
// 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
Python
Python
C++
// This is not yet supported.
Node.js
Go
PHP
PHP
Pour en savoir plus sur l'installation et la création d'un client Cloud Firestore, consultez la page Bibliothèques clientes Cloud Firestore.
Unity
Query query1 = db.Collection("cities").OrderBy("Name").OrderBy("State").StartAt("Springfield"); Query query2 = db.Collection("cities").OrderBy("Name").OrderBy("State").StartAt("Springfield", "Missouri");