数据库（输入阶段）

数据库（输入阶段）

说明

返回数据库中不同集合和嵌套级别中的所有文档。

示例

Web

// Count all documents in the database
const results = await execute(db.pipeline()
  .database()
  .aggregate(countAll().as("total"))
  );
test.firestore.js

Swift

// Count all documents in the database
let results = try await db.pipeline()
  .database()
  .aggregate([CountAll().as("total")])
  .execute()
PipelineSnippets.swift

Kotlin
Android

// Count all documents in the database
val results = db.pipeline()
    .database()
    .aggregate(AggregateFunction.countAll().alias("total"))
    .execute()
DocSnippets.kt

Java
Android

      // Count all documents in the database
Task<Pipeline.Snapshot> results = db.pipeline()
    .database()
    .aggregate(AggregateFunction.countAll().alias("total"))
    .execute();
DocSnippets.java
    

Python

from google.cloud.firestore_v1.pipeline_expressions import Count

# Count all documents in the database
results = client.pipeline().database().aggregate(Count().as_("total")).execute()
firestore_pipelines.py

Java

// Count all documents in the database
Pipeline.Snapshot results =
    firestore.pipeline().database().aggregate(countAll().as("total")).execute().get();
PipelineSnippets.java

行为

如需使用 database(...) 阶段，它必须作为流水线中的第一个阶段出现。

从 database(...) 阶段返回的文档顺序不稳定，不能依赖。可使用后续的 sort(...) 阶段 来获得确定性的顺序。

例如，对于以下文档：

Node.js

await db.collection("cities").doc("SF").set({name: "San Francsico", state: "California", population: 800000});
await db.collection("states").doc("CA").set({name: "California", population: 39000000});
await db.collection("countries").doc("USA").set({name: "United States of America", population: 340000000});

database(...) 阶段可用于检索数据库中的所有文档。

Node.js

const results = await db.pipeline()
  .database()
  .sort(field("population").ascending())
  .execute();

此查询会生成以下文档：

  { name: "San Francsico", state: "California", population: 800000 }
  { name: "California", population: 39000000 }
  { name: "United States of America", population: 340000000 }