集合组

说明

返回具有指定集合 ID 的任何集合中的所有文档，无论其父级是什么。

语法

Node.js

const results = await db.pipeline()
  .collectionGroup('departments')
  .execute();

行为

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

从 collection_group 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/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});

collection_group 阶段可用于返回数据库中所有父集合下的各个部门集合内的所有文档。

Node.js

const results = await db.pipeline()
  .collectionGroup('departments')
  .sort(field('employees').ascending())
  .execute();

此查询会生成以下文档：

  {name: 'SF Building Deparment', employees: 750}
  {name: 'CHI Building Deparment', employees: 900}
  {name: 'NY Building Deparment', employees: 1000}
  {name: 'NY Finance Deparment', employees: 1200}

更多示例

Web

const results = await execute(db.pipeline()
  .collectionGroup("games")
  .sort(field("name").ascending())
  );
test.firestore.js

Swift
let results = try await db.pipeline()
  .collectionGroup("games")
  .sort([Field("name").ascending()])
  .execute()
PipelineSnippets.swift

Kotlin

val results = db.pipeline()
    .collectionGroup("games")
    .sort(field("name").ascending())
    .execute()
DocSnippets.kt

Java

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

results = (
    client.pipeline()
    .collection_group("games")
    .sort(Field.of("name").ascending())
    .execute()
)
firestore_pipelines.py