数据库

说明

返回数据库中不同集合和嵌套级别中的所有文档。

语法

Node.js

const results = await db.pipeline()
  .database()
  .execute();

客户端示例

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

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

Java

// 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")).execut
e().get();PipelineSni
ppets.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，不应依赖。可使用后续的排序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}