How to find documents with multiple conditions using mongo-driver/mongo - mongodb

Question

While querying the below data, returned cursor is empty. while there is 100s of documents which satisfy the condition.
{
"_id": "5dd68c51a39809125944ffba",
"status": "success",
"balance": "0.000",
"request_params": {
"username": "test_user",
"service_code": "MR"
}
using below code
MongoDB driver "go.mongodb.org/mongo-driver/mongo"
func saveLog(data Log) bool {
mongo, err := openMongo()
if err != nil {
log.Println(err)
fmt.Println("Connection failed")
return false
} else {
LogCollection := mongo.Database(LogDb).Collection(CollectionLog)
insertedApi, err := LogCollection.InsertOne(context.TODO(), data)
if err != nil {
log.Println(err)
fmt.Println("Insert failed")
return false
} else {
log.Println(insertedApi.InsertedID)
return true
}
}
}
func parseLog() {
db, err := openMongo()
if err != nil {
fmt.Println(err)
fmt.Println("Connection failed")
return
} else {
logCollection := db.Database(LogDb).Collection(CollectionLog)
var results [] *Log
find := bson.D{{"status","success"},{"request_params",bson.D{{"username","test_user"}}}}
fmt.Println(find)
cur, err := logCollection.Find(context.TODO(), find)
if err != nil {
log.Fatal(err)
}else {
for cur.Next(context.TODO()) {
var elem Log
err := cur.Decode(&elem)
if err != nil {
fmt.Println("Parse error : ",err)
}
fmt.Println("Log : ",elem)
results = append(results, &elem)
}
}
}
}
Log write
saveLog(Log{"success","0.000",RequestParams{"test_user","MR"}})
Log read
parseLog()
Log struct
type Log struct {
Status string `bson:"status"`
Balance string `bson:"balance"`
RequestParams RequestParams `bson:"request_params"`
}
type RequestParams struct {
Username string `bson:"username"`
ServiceCode string `bson:"service_code"`
}
MongoDB data
status only is returning whole 8k documents
bson.D{{"status","success"}}
Isn't collection.Find() function the right one for it.
Shell command is returning documents correctly
db.log.find({"status":"success","request_params.username":"test_user"}).limit(10).pretty()

Answer 1

The issue here is because of the query filter. There is a difference between the following queries:
// Query A: {"status": "success", "request_params": {"username":"test_user"}}
find := bson.D{{"status","success"},{"request_params",bson.D{{"username","test_user"}}}}
// Query B: {"status": "success", "request_params.username":"test_user"}
find := bson.D{{"status","success"},{"request_params.username","test_user"}}
Query A means that you would like to match an exact document of request_params where the value object exactly equal to {"username":"test_user"}. None of the documents in your collection matches this criteria. The documents also contains {"service_code":"MR"}. While query B uses dot notation, which means that you would like to match request_params field where it contains a value of {"username":"test_user"}.
See also Query on Nested Field for more information.