文件集

說明

傳回指定集合中的所有文件。集合可以巢狀結構。

範例

Web

const results = await execute(db.pipeline()
  .collection("users/bob/games")
  .sort(field("name").ascending())
  );
Swift
let results = try await db.pipeline()
  .collection("users/bob/games")
  .sort([Field("name").ascending()])
  .execute()

Kotlin

val results = db.pipeline()
    .collection("users/bob/games")
    .sort(field("name").ascending())
    .execute()

Java

Task<Pipeline.Snapshot> results = db.pipeline()
    .collection("users/bob/games")
    .sort(field("name").ascending())
    .execute();
Python
from google.cloud.firestore_v1.pipeline_expressions import Field

results = (
    client.pipeline()
    .collection("users/bob/games")
    .sort(Field.of("name").ascending())
    .execute()
)
Java
Pipeline.Snapshot results =
    firestore
        .pipeline()
        .collection("users/bob/games")
        .sort(ascending(field("name")))
        .execute()
        .get();
Go
snapshot := client.Pipeline().
	Collection("users/bob/games").
	Sort(firestore.Orders(firestore.Ascending(firestore.FieldOf("name")))).
	Execute(ctx)

行為

如要使用 collection(...) 階段，該階段必須是管道 (或子管道) 中的第一個階段。

從 collection(...) 階段傳回的文件順序不穩定，因此不建議依此排序。Firestore 會盡可能以最有效率的方式執行查詢，因此順序可能會因結構定義或索引設定而異。後續的 sort(...) 階段可用於取得確定性排序。

舉例來說，下列文件：

Node.js

await db.collection("cities").doc("SF").set({name: "San Francsico", state: "California"});
await db.collection("cities").doc("NYC").set({name: "New York City", state: "New York"});
await db.collection("cities").doc("CHI").set({name: "Chicago", state: "Illinois"});
await db.collection("states").doc("CA").set({name: "California"});

collection 階段可用於擷取 cities 集合中的所有城市，然後依名稱遞增排序。

Node.js

const results = await db.pipeline()
  .collection("/cities")
  .sort(field("name").ascending())
  .execute();

這項查詢會產生下列文件：

  { name: "Chicago", state: "Illinois" }
  { name: "New York City", state: "New York" }
  { name: "San Francisco", state: "California" }

子集合

您也可以提供階段的完整路徑，藉此指定特定父項下的集合。collection(...)

舉例來說，下列文件：

Node.js

await db.collection("cities/SF/departments").doc("building").set({name: "SF Building Deparment", employees: 750});
await db.collection("cities/NY/departments").doc("building").set({name: "NY Building Deparment", employees: 1000});
await db.collection("cities/CHI/departments").doc("building").set({name: "CHI Building Deparment", employees: 900});
await db.collection("cities/NY/departments").doc("finance").set({name: "NY Finance Deparment", employees: 1200});

在本例中，我們只想要紐約市的部門。

Node.js

const results = await db.pipeline()
  .collection("/cities/NY/departments")
  .sort(field("employees").ascending())
  .execute();

這會傳回完整路徑 cities/NY/departments 下的所有部門。

  { name: "NY Building Deparment", employees: 1000 }
  { name: "NY Finance Deparment", employees: 1200 }