使用查询游标将数据分页

通过在 Cloud Firestore 中使用查询游标，您可以根据在查询中定义的参数将返回的数据分成多个批次。

查询游标定义了查询的起点和终点，并让您可以：

  • 返回数据的子集。
  • 将查询结果分页。

但是，如需为查询定义特定的范围，您应该使用 where() 方法（具体说明请参阅简单查询）。

向查询中添加简单游标

使用 startAt() 或 startAfter() 方法定义查询的起点。startAt() 方法包含起点，而 startAfter() 方法则不包含起点。

例如，如果您在查询中使用 startAt(A)，该查询会返回整个字母表。如果您改为使用 startAfter(A)，则该查询会返回 B-Z。

Web

import { query, orderBy, startAt } from "firebase/firestore";  

const q = query(citiesRef, orderBy("population"), startAt(1000000));
order_and_start.js

Web

citiesRef.orderBy("population").startAt(1000000);
test.firestore.js
Swift
注意：此产品不适用于 watchOS 和 App Clip 目标。 
// Get all cities with population over one million, ordered by population.
db.collection("cities")
  .order(by: "population")
  .start(at: [1000000])
ViewController.swift
Objective-C
注意：此产品不适用于 watchOS 和 App Clip 目标。 
// Get all cities with population over one million, ordered by population.
[[[db collectionWithPath:@"cities"]
    queryOrderedByField:@"population"]
    queryStartingAtValues:@[ @1000000 ]];
ViewController.m

Kotlin+KTX

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

Java

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

Dart

db.collection("cities").orderBy("population").startAt([1000000]);
firestore.dart
Java
Query query = cities.orderBy("population").startAt(4921000L);
QueryDataSnippets.java
Python
cities_ref = db.collection("cities")
query_start_at = cities_ref.order_by("population").start_at({"population": 1000000})
snippets.py

Python

cities_ref = db.collection("cities")
query_start_at = cities_ref.order_by("population").start_at({"population": 1000000})
snippets.py
C++
// Get all cities with a population >= 1,000,000, ordered by population,
db->Collection("cities")
    .OrderBy("population")
    .StartAt({FieldValue::Integer(1000000)});
snippets.cpp
Node.js
const startAtRes = await db.collection('cities')
  .orderBy('population')
  .startAt(1000000)
  .get();
index.js
Go
query := client.Collection("cities").OrderBy("population", firestore.Asc).StartAt(1000000)
query.go
PHP

PHP

如需详细了解如何安装和创建 Cloud Firestore 客户端，请参阅 Cloud Firestore 客户端库。 

$query = $citiesRef
    ->orderBy('population')
    ->startAt([1000000]);
query_cursor_start_at_field_value_single.php
Unity
Query query = citiesRef.OrderBy("Population").StartAt(1000000);
C#
Query query = citiesRef.OrderBy("Population").StartAt(1000000);
Program.cs
Ruby
query = cities_ref.order("population").start_at(1_000_000)
paginate_data.rb

同样，可使用 endAt() 或 endBefore() 方法定义查询结果的终点。

Web

import { query, orderBy, endAt } from "firebase/firestore";  

const q = query(citiesRef, orderBy("population"), endAt(1000000));
order_and_end.js

Web

citiesRef.orderBy("population").endAt(1000000);
test.firestore.js
Swift
注意：此产品不适用于 watchOS 和 App Clip 目标。 
// Get all cities with population less than one million, ordered by population.
db.collection("cities")
  .order(by: "population")
  .end(at: [1000000])
ViewController.swift
Objective-C
注意：此产品不适用于 watchOS 和 App Clip 目标。 
// Get all cities with population less than one million, ordered by population.
[[[db collectionWithPath:@"cities"]
    queryOrderedByField:@"population"]
    queryEndingAtValues:@[ @1000000 ]];
ViewController.m

Kotlin+KTX

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

Java

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

Dart

db.collection("cities").orderBy("population").endAt([1000000]);
firestore.dart
Java
Query query = cities.orderBy("population").endAt(4921000L);
QueryDataSnippets.java
Python
cities_ref = db.collection("cities")
query_end_at = cities_ref.order_by("population").end_at({"population": 1000000})
snippets.py

Python

cities_ref = db.collection("cities")
query_end_at = cities_ref.order_by("population").end_at({"population": 1000000})
snippets.py
C++
// Get all cities with a population <= 1,000,000, ordered by population,
db->Collection("cities")
    .OrderBy("population")
    .EndAt({FieldValue::Integer(1000000)});
snippets.cpp
Node.js
const endAtRes = await db.collection('cities')
  .orderBy('population')
  .endAt(1000000)
  .get();
index.js
Go
query := client.Collection("cities").OrderBy("population", firestore.Asc).EndAt(1000000)
query.go
PHP

PHP

如需详细了解如何安装和创建 Cloud Firestore 客户端，请参阅 Cloud Firestore 客户端库。 

$query = $citiesRef
    ->orderBy('population')
    ->endAt([1000000]);
query_cursor_end_at_field_value_single.php
Unity
Query query = citiesRef.OrderBy("Population").EndAt(1000000);
C#
Query query = citiesRef.OrderBy("Population").EndAt(1000000);
Program.cs
Ruby
query = cities_ref.order("population").end_at(1_000_000)
paginate_data.rb

使用文档快照定义查询游标

您还可以将文档快照传递给游标子句，将其用作查询游标的起点或终点。文档快照中的值充当查询游标中的值。

例如，在城市和人口数据集中，创建“旧金山”文档的快照。然后，使用该文档快照作为人口查询游标的起点。查询将返回人口不少于旧金山市的所有城市，如文档快照中所定义。

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));
// ...
start_doc.js

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);

    // ...
});
test.firestore.js
Swift
注意：此产品不适用于 watchOS 和 App Clip 目标。 
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)
  }
ViewController.swift
Objective-C
注意：此产品不适用于 watchOS 和 App Clip 目标。 
[[[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];
    }];
ViewController.m

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)

        // ...
    }
DocSnippets.kt

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);

                // ...
            }
        });
DocSnippets.java

Dart

db.collection("cities").doc("SF").get().then(
  (documentSnapshot) {
    final biggerThanSf = db
        .collection("cities")
        .orderBy("population")
        .startAtDocument(documentSnapshot);
  },
  onError: (e) => print("Error: $e"),
);
firestore.dart
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);
QueryDataSnippets.java
Python
doc_ref = db.collection("cities").document("SF")

snapshot = doc_ref.get()
start_at_snapshot = (
    db.collection("cities").order_by("population").start_at(snapshot)
)
snippets.py

Python

doc_ref = db.collection("cities").document("SF")

snapshot = await doc_ref.get()
start_at_snapshot = (
    db.collection("cities").order_by("population").start_at(snapshot)
)
snippets.py
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});
        // ...
      }
    });
snippets.cpp
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();
index.js
Go
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)
query.go
PHP

PHP

如需详细了解如何安装和创建 Cloud Firestore 客户端，请参阅 Cloud Firestore 客户端库。 

$citiesRef = $db->collection('samples/php/cities');
$docRef = $citiesRef->document('SF');
$snapshot = $docRef->snapshot();

$query = $citiesRef
    ->orderBy('population')
    ->startAt($snapshot);
query_cursor_start_at_document.php
Unity
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);
Program.cs
Ruby
doc_ref = firestore.doc "#{collection_path}/SF"
snapshot = doc_ref.get
query = cities_ref.order("population").start_at(snapshot)
paginate_data.rb

对查询结果进行分页

通过将查询游标与 limit() 方法结合使用，可将查询分页。例如，使用某批文档中的最后一个文档作为下一批文档的游标起点。

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));
paginate.js

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);
});
test.firestore.js
Swift
注意：此产品不适用于 watchOS 和 App Clip 目标。 
// 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.
  // ...
}
ViewController.swift
Objective-C
注意：此产品不适用于 watchOS 和 App Clip 目标。 
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.
  // ...
}];
ViewController.m

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
        // ...
    }
DocSnippets.kt

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
            // ...
        }
    });
DocSnippets.java

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"),
);
firestore.dart
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();
QueryDataSnippets.java
Python
cities_ref = db.collection("cities")
first_query = cities_ref.order_by("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()["population"]

next_query = (
    cities_ref.order_by("population").start_after({"population": last_pop}).limit(3)
)
# Use the query for pagination
# ...
snippets.py

Python

cities_ref = db.collection("cities")
first_query = cities_ref.order_by("population").limit(3)

# Get the last document from the results
docs = [d async for d in 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()["population"]

next_query = (
    cities_ref.order_by("population").start_after({"population": last_pop}).limit(3)
)
# Use the query for pagination
# ...
snippets.py
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
  // ...
});
snippets.cpp
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
// ...
index.js
Go
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)

// ...
query.go
PHP

PHP

如需详细了解如何安装和创建 Cloud Firestore 客户端，请参阅 Cloud Firestore 客户端库。 

$citiesRef = $db->collection('samples/php/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();
query_cursor_pagination.php
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#
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();
Program.cs
Ruby
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
paginate_data.rb

基于多个字段设置游标

使用基于某个字段值（而非 DocumentSnapshot）的游标时，您可以添加其他字段，使游标位置更加精确。当您的数据集包含多个具有与游标字段相同值的文档，造成游标位置不明确时，尤其需要使用该功能。 您可以为游标添加其他字段值，以便进一步指明起点或终点，并减少歧义。

例如，在包含美国所有名为“斯普林菲尔德”的城市的数据集中，起点设为“斯普林菲尔德”的查询将有多个起点：

城市
名称 州
Springfield 马萨诸塞
Springfield 密苏里
Springfield 威斯康星

要以某个特定的斯普林菲尔德市作为起点，您可以在游标子句中添加州作为次要条件。

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"));
start_multiple_orderby.js

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");
test.firestore.js
Swift
注意：此产品不适用于 watchOS 和 App Clip 目标。 
// 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"])
ViewController.swift
Objective-C
注意：此产品不适用于 watchOS 和 App Clip 目标。 
// 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" ]];
ViewController.m

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")
DocSnippets.kt

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");
DocSnippets.java

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"]);
firestore.dart
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");
QueryDataSnippets.java
Python
start_at_name = (
    db.collection("cities").order_by("name").start_at({"name": "Springfield"})
)

start_at_name_and_state = (
    db.collection("cities")
    .order_by("name")
    .order_by("state")
    .start_at({"name": "Springfield", "state": "Missouri"})
)
snippets.py

Python

start_at_name = (
    db.collection("cities")
    .order_by("name")
    .order_by("state")
    .start_at({"name": "Springfield"})
)

start_at_name_and_state = (
    db.collection("cities")
    .order_by("name")
    .order_by("state")
    .start_at({"name": "Springfield", "state": "Missouri"})
)
snippets.py
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();
index.js
Go
// 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")
query.go
PHP

PHP

如需详细了解如何安装和创建 Cloud Firestore 客户端，请参阅 Cloud Firestore 客户端库。 

// Will return all Springfields
$query1 = $db
    ->collection('samples/php/cities')
    ->orderBy('name')
    ->orderBy('state')
    ->startAt(['Springfield']);

// Will return "Springfield, Missouri" and "Springfield, Wisconsin"
$query2 = $db
    ->collection('samples/php/cities')
    ->orderBy('name')
    ->orderBy('state')
    ->startAt(['Springfield', 'Missouri']);
query_cursor_start_at_field_value_multi.php
Unity
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");
Program.cs
Ruby
# 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"])
paginate_data.rb