db.command.aggregate.push
#
1. 操作符描述功能:在 group
阶段,返回一组中表达式指定列与对应的值,一起组成的数组。
声明:db.command.aggregate.push({ <字段名1>: <指定字段1>, <字段名2>: <指定字段2>, ... })
#
2. 操作符参数字段 | 类型 | 必填 | 说明 |
---|---|---|---|
- | Object | 是 | 对象键值为任意聚合表达式 |
#
3. 示例代码假设集合 students
的记录如下:
{ "group": "a", "name": "stu1", "score": 84 }{ "group": "a", "name": "stu2", "score": 96 }{ "group": "b", "name": "stu3", "score": 80 }{ "group": "b", "name": "stu4", "score": 100 }
借助 push
操作,对不同分组( group
)的所有记录,聚合所有数据并且将其放入一个新的字段中,进一步结构化和语义化数据。
// 云函数环境下示例代码const tcb = require('@cloudbase/node-sdk')const app = tcb.init({ env: 'xxx'})
const db = app.database()const $ = db.command.aggregateconst _ = db.command
exports.main = async (event, context) => { const res = await db .collection('students') .aggregate() .group({ _id: '$group', students: $.push({ name: '$name', score: '$score' }) }) .end() console.log(res.data)}
输出结果如下:
{ "_id": "b", "students": [{ "name": "stu3", "score": 80 }, { "name": "stu4", "score": 100 }] }{ "_id": "a", "students": [{ "name": "stu1", "score": 84 }, { "name": "stu2", "score": 96 }] }