如何在 mongo golang 驱动程序中使用聚合 $facet 查询答案

【问题标题】：How to use aggregate $facet query with mongo golang driver如何在 mongo golang 驱动程序中使用聚合 $facet 查询
【发布时间】：2020-09-01 00:39:40
【问题描述】：

如何使用 mongo golang 驱动程序将以下查询转换为管道

db.transFront.aggregate([
{
        $facet: {
            query1: [ { $match: { appName:"app-38" }}, { $count: "count" }],
            query2: [ { $match: { appName:"app-43" }}, { $count: "count" } ],
            query3: [ { $match: { appName:"app--1" }}, { $count: "count" } ],
        }
    }
])

【问题讨论】：

标签： mongodb go

【解决方案1】：

要在 go lang MongoDB 驱动程序中运行 $facet，请使用以下代码，只需替换您的连接字符串和数据库名称

package main

import (
    "context"
    "time"
    "fmt"
    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

func main() {
    ctx, _ := context.WithTimeout(context.Background(), 10*time.Second)
    client, err := mongo.Connect(ctx, options.Client().ApplyURI("mongodb_connect_string"))
    if err != nil {
        panic(err)
    }
    defer client.Disconnect(ctx)

    database := client.Database("testdb")
    transFront := database.Collection("transFront")



    query1 := bson.A{bson.D{{"$match", bson.D{{"appName", "app-38"}}}}, bson.D{{"$count", "count"}}}
    query2 := bson.A{bson.D{{"$match", bson.D{{"appName", "app-43"}}}}, bson.D{{"$count", "count"}}}
    query3 := bson.A{bson.D{{"$match", bson.D{{"appName", "app--1"}}}}, bson.D{{"$count", "count"}}}

    facetStage := bson.D{{"$facet", bson.D{{"query1", query1}, {"query2", query2}, {"query3", query3}}}}

    showInfoCursor, err := transFront.Aggregate(ctx, mongo.Pipeline{facetStage})
    if err != nil {
            panic(err)
    }
    var showsWithInfo []bson.M
    if err = showInfoCursor.All(ctx, &showsWithInfo); err != nil {
            panic(err)
    }

    fmt.Println(showsWithInfo)
}

【讨论】：

乐于助人:)