Need help in getting an element from mongodb document and updating its value using go mongo drivers

Hey there I am using the go.mongodb.org/mongo-driver package to work with golang. This is my code:

package src

import (
	"context"
	"fmt"
	"log"

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

var (
	client      *mongo.Client
	stickerscol *mongo.Collection
)

func init() {
	log.Println("Setting up database...")
	var err error
	client, err = mongo.Connect(context.Background(), options.Client().ApplyURI(Envars.DbUrl))
	if err != nil {
		log.Fatal(err)
	}
	log.Println("Connected to database")
	stickerscol = client.Database("stickersbot").Collection("stickers")
	chatcol = client.Database("stickersbot").Collection("chat")
}

func ChangeDefaultPack(userid int64, stickername string, format string) error {
	fmt.Println(userid, stickername, format)
	filter := bson.M{
		"_id":                      userid,
		"stickers.stickername":     stickername,
		"stickers.stickerpacktype": format,
	}
	updateOther := bson.M{
		"$set": bson.M{
			"stickers.$[elem].isdefault": false,
		},
	}
	update := bson.M{
		"$set": bson.M{
			"stickers.$.isdefault": true,
		},
	}
	arrayFilters := options.ArrayFilters{
		Filters: []interface{}{bson.M{"elem.stickerpacktype": format}},
	}
	updateOptions := options.Update().SetArrayFilters(arrayFilters)
	_, err := stickerscol.UpdateMany(context.TODO(), filter, updateOther, updateOptions)
	if err != nil {
		return err
	}
	ok, err := stickerscol.UpdateOne(context.Background(), filter, update, options.Update().SetUpsert(true))
	if err != nil {
		return err
	}
	if ok.ModifiedCount == 0 {
		fmt.Println("no document matched")
		return fmt.Errorf("no document matched")
	}
	return err
}

And this is the db structure:

...
{
"_id": 1633375527,
"stickers": [
{
"stickerpacktype": "static",
"stickername": "gVtOy_1633375527_by_ChadManBot",
"isdefault": true
},
{
"stickerpacktype": "animated",
"stickername": "zIjsa_1633375527_by_ChadManBot",
"isdefault": true
},
{
"stickerpacktype": "video",
"stickername": "bJBle_1633375527_by_ChadManBot",
"isdefault": true
},
{
"stickerpacktype": "static",
"stickername": "iujiw_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "video",
"stickername": "CHnqb_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "XKJUP_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "animated",
"stickername": "pCFlC_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "animated",
"stickername": "jGGgt_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "animated",
"stickername": "cTxyA_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "animated",
"stickername": "ZfYXO_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "xJUkA_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "HIvsY_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "WIHFQ_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "OqjtE_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "QNysO_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "OrTsT_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "FzROg_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "QUBcT_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "NsZfM_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "AkxVM_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "Ddvus_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "LXfHV_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "sTaMv_1633375527_by_ChadManBot",
"isdefault": false
},
{
"stickerpacktype": "static",
"stickername": "vppgK_1633375527_by_ChadManBot",
"isdefault": false
}
],
"stickerpackcount": 2
}
...

What I need my code is to find list of sticker packs which matches the given id and sticker type and set their default value to false and set the default value of the pack which is passed to the func as true.

Basically just making one as default and others as not default. Could someone explain me why this function is returning no document found?

When there are multiple field matches, you should use the $elemMatch operator. Otherwise, the $ operator does not work. See Update Embedded Documents Using Multiple Field Matches.

And you don't need UpdateMany to update multiple array elements in a single document. Use UpdateOne instead.

Here is the demo based on your code and data:

package main

import (
	"context"
	"fmt"
	"log"

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

var (
	client      *mongo.Client
	stickerscol *mongo.Collection
)

func init() {
	log.Println("Setting up database...")
	var err error
	client, err = mongo.Connect(context.Background(), options.Client().ApplyURI("mongodb://localhost"))
	if err != nil {
		log.Fatal(err)
	}
	log.Println("Connected to database")
	stickerscol = client.Database("stickersbot").Collection("stickers")
}

func ChangeDefaultPack(userid int64, stickername string, format string) error {
	fmt.Println(userid, stickername, format)
	filter := bson.M{
		"_id": userid,
		"stickers": bson.M{
			"$elemMatch": bson.M{
				"stickername":     stickername,
				"stickerpacktype": format,
			},
		},
	}
	updateOther := bson.M{
		"$set": bson.M{
			"stickers.$[elem].isdefault": false,
		},
	}
	arrayFilters := options.ArrayFilters{
		Filters: []interface{}{bson.M{"elem.stickerpacktype": format}},
	}
	updateOptions := options.Update().SetArrayFilters(arrayFilters)
	result, err := stickerscol.UpdateOne(context.Background(), filter, updateOther, updateOptions)
	if err != nil {
		return err
	}
	log.Printf("update other: %+v\n", result)

	update := bson.M{
		"$set": bson.M{
			"stickers.$.isdefault": true,
		},
	}
	ok, err := stickerscol.UpdateOne(context.Background(), filter, update, options.Update().SetUpsert(true))
	if err != nil {
		return err
	}
	log.Printf("update default: %+v\n", ok)
	if ok.ModifiedCount == 0 {
		fmt.Println("no document matched")
		return fmt.Errorf("no document matched")
	}
	return err
}

func main() {
	if err := ChangeDefaultPack(1633375527, "Ddvus_1633375527_by_ChadManBot", "static"); err != nil {
		panic(err)
	}
}

Run the demo and you will observe the following change to the document:

--- before.json	2023-06-27 00:34:32.721978745 +0800
+++ after.json	2023-06-27 00:34:59.489836137 +0800
@@ -4,7 +4,7 @@
     {
       "stickerpacktype": "static",
       "stickername": "gVtOy_1633375527_by_ChadManBot",
-      "isdefault": true
+      "isdefault": false
     },
     {
       "stickerpacktype": "animated",
@@ -104,7 +104,7 @@
     {
       "stickerpacktype": "static",
       "stickername": "Ddvus_1633375527_by_ChadManBot",
-      "isdefault": false
+      "isdefault": true
     },
     {
       "stickerpacktype": "static",