golang mongodb 分组sort 取第一个

usefull urls

https://blog.csdn.net/weixin_46124208/article/details/108483355

> db.sales.find()
{ "_id" : ObjectId("77f02ee61df85c423b6a4e79"), "client" : "1", "type" : "type1", "hierarchy" : "hier1", "creationDate" : ISODate("2015-09-09T13:06:44Z"), "model" : "m1" }
{ "_id" : ObjectId("77f02ee61df85c423b6a4e80"), "client" : "1", "type" : "type1", "hierarchy" : "hier1", "creationDate" : ISODate("2015-09-10T14:06:44Z"), "model" : "m2" }
{ "_id" : ObjectId("77f02ee61df85c423b6a4e81"), "client" : "1", "type" : "type1", "hierarchy" : "hier2", "creationDate" : ISODate("2015-09-10T13:06:44Z"), "model" : "m3" }
{ "_id" : ObjectId("77f02ee61df85c423b6a4e82"), "client" : "2", "type" : "type2", "hierarchy" : "hier2", "creationDate" : ISODate("2015-09-10T14:06:44Z"), "model" : "m4" }

//mongo 原始语句

db.sales.aggregate([
{$match:{$or:[{"client":"1"},{"client":"2"}]}},
{$sort:{"creationDate":1}},
{$group:{"_id":{"hierarchy":"$hierarchy"},"record":{$first:"$$ROOT"}}},
{$project:{"_id":"$record._id","client":"$record.client","hierarchy":"$record.hierarchy","creationDate":"$record.creationDate"}}
]);

package main

import (
    "context"
    "fmt"
    "strings"
    "time"

    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)


func MongoPipeline(str string) mongo.Pipeline {
    var pipeline = []bson.D{}
    str = strings.TrimSpace(str)
    if strings.Index(str, "[") != 0 {
        var doc bson.D
        bson.UnmarshalExtJSON([]byte(str), false, &doc)
        pipeline = append(pipeline, doc)
    } else {
        bson.UnmarshalExtJSON([]byte(str), false, &pipeline)
    }
    return pipeline
}

func main() {
    ctx, _ := context.WithTimeout(context.Background(), 10*time.Second)
    client, err := mongo.Connect(ctx, options.Client().ApplyURI("mongodb://1.1.13.10:27017"))
    if err != nil {
        panic(err)
    }
    defer client.Disconnect(ctx)

    database := client.Database("huzh")
    episodesCollection := database.Collection("sales")
    opts := options.Aggregate()
    //id, _ := primitive.ObjectIDFromHex("5e3b37e51c9d4400004117e6")
    //
    //matchStage := bson.D{{"$match", bson.D{{"podcast", id}}}}
    //groupStage := bson.D{{"$group", bson.D{{"_id", "$podcast"}, {"total", bson.D{{"$sum", "$duration"}}}}}}

    //id, _ := primitive.ObjectIDFromHex("5e3b37e51c9d4400004117e6")


//    pipeline := `
//[
//{$match:{$or:[{"client":"1"},{"client":"2"}]}},
//{$group:{"_id":{"hierarchy":"$hierarchy"},"record":{$first:"$$ROOT"}}},
//{$project:{"_id":0}}
//]`

var rb []bson.M
    rb = []bson.M{bson.M{"client": "1"}, bson.M{"client": "2"}}
    fmt.Println(rb)
    pipeline := mongo.Pipeline{
        bson.D{
            {"$match", bson.M{"$or":rb}},
            //{"$match", bson.M{"$or":[]bson.M{bson.M{"client": "1"}, bson.M{"client": "2"}}}},
        },
        bson.D{
            {"$sort", bson.D{{"creationDate", -1}}},
        },
        bson.D{
            {"$group", bson.D{
                //{"_id", "$betarea"},
                //{"sum", bson.D{{"$sum", "$amount"}}},
                //{"count", bson.D{{"$sum", 1}}},
                {"_id", bson.D{{"hierarchy", "$hierarchy"}}},
                {"record", bson.D{{"$first", "$$ROOT"}}},
            }},
        },
        bson.D{
            {"$project", bson.M{"_id":"$record._id","client":"$record.client","hierarchy":"$record.hierarchy","creationDate":"$record.creationDate"}},
        },


    }

    //showInfoCursor, err := episodesCollection.Aggregate(ctx,  MongoPipeline(pipeline),opts)
    showInfoCursor, err := episodesCollection.Aggregate(ctx,  pipeline,opts)
    //fmt.Println(showInfoCursor)
    if err != nil {
        panic(err)
    }
    var showsWithInfo []bson.M
    if err = showInfoCursor.All(ctx, &showsWithInfo); err != nil {
        panic(err)
    }
    fmt.Println(showsWithInfo)
    fmt.Println(len(showsWithInfo))
}