Mongodb pipeline example

main.go

package main

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

type OrderStatusTotal struct {
	ID string `bson:"_id"`
	Total int `bson:"total"`
}

func main(){
	client, err := mongo.NewClient(options.Client().ApplyURI("mongodb://localhost:27017"))
	if err != nil {
		fmt.Errorf("failed to create a mongo client %s", err.Error())
		log.Println(err.Error())
		return
	}

	ctx, _ := context.WithTimeout(context.Background(), 1*time.Second)
	collection := client.Database("ecomerce").Collection("orders")

	err = client.Connect(ctx)
	if err != nil {
		log.Println(err.Error())
		fmt.Errorf("connection to mongodb failed %s", err.Error())
		return
	}

	pipelineResult := make([]OrderStatusTotal, 0)

	pipeline := make([]bson.M, 0)

	groupStage := bson.M{
		"$group": bson.M{
		"_id": "$status",
		"total": bson.M{"$sum": 1},
		},
	}

	matchStage := bson.M{
		"$match": bson.M{
			"cust_id": "abc1",
		},
	}

	pipeline = append(pipeline, matchStage,groupStage)

	data, err := collection.Aggregate(ctx, pipeline)
	if err != nil {
		log.Println(err.Error())
		fmt.Errorf("failed to execute aggregation %s", err.Error())
		return
	}

	err = data.All(ctx, &pipelineResult)
	if err != nil {
		log.Println(err.Error())
		fmt.Errorf("failed to decode results", err.Error())
		return
	}

	fmt.Printf("%+v\n", pipelineResult)

}