Dynamically insert multiple documents using mgo golang mongodb - database

Question

How can I insert an array of documents into MongoDB with mgo library using only a single DB call as in db.collection.insert()?
I have the following Transaction structure:
type Transaction struct {
Brand string `json:"brand"`
Name string `json:"name"`
Plu string `json:"plu"`
Price string `json:"price"`
}
From a POST request I will recieve an array of these structures. I want to insert them into MongoDB as individual documents but using a single DB call as explained in db.collection.insert()
I tried using c.Insert of mgo
The following is the code snippet:
func insertTransaction(c *gin.Context) {
var transactions []Transaction
err := c.BindJSON(&transactions)
if err != nil {
c.AbortWithStatusJSON(http.StatusBadRequest, map[string]string{"error":"invalid JSON"})
return
}
err = InsertTransactons(transactions)
if err != nil {
c.AbortWithStatusJSON(http.StatusInternalServerError, &map[string](interface{}){
"status": "error",
"code": "500",
"message": "Internal server error",
"error": err,
})
return
}
c.JSON(http.StatusCreated, &map[string](interface{}){
"status": "success",
"code": "0",
"message": "created",
})
}
func InsertTransactons(u []Transaction) error {
s := GetSession()
defer s.Close()
c := s.DB(DB).C(TransactionColl)
err := c.Insert(u...)
if err != nil {
return err
}
return nil
}
But as I compile and run the code, I get the following error:
go/database.go:34:17: cannot use u (type *[]Transaction) as type
[]interface {} in argument to c.Insert

Answer 1

You cannot pass []*Transaction as []interface{}. You need to convert each Transaction to inferface{} to change its memory layout.
var ui []interface{}
for _, t := range u{
ui = append(ui, t)
}
Pass ui to c.Insert instead

Answer 2

Create slice of interface for document structs by appending and then inserting data using Bulk insert which takes variable arguments.
type Bulk struct {
// contains filtered or unexported fields
}
func (b *Bulk) Insert(docs ...interface{})
For inserting documents in Bulk
const INSERT_COUNT int = 10000
type User struct {
Id bson.ObjectId `bson:"_id,omitempty" json:"_id"`
Email string `bson:"email" json:"email"`
}
func (self *User) Init() {
self.Id = bson.NewObjectId()
}
Call Bulk() function on collection returned from db connection. Bulk() function returns pointer to *Bulk.
bulk := dbs.Clone().DB("").C("users").Bulk()
bulk.Insert(users...)
Assign it to variable which will be used to call Insert() method using Bulk pointer receiver.
func main(){
// Database
dbs, err := mgo.Dial("mongodb://localhost/")
if err != nil {
panic(err)
}
// Collections
uc := dbs.Clone().DB("").C("users")
defer dbs.Clone().DB("").Session.Close()
for n := 0; n < b.N; n++ {
count := INSERT_COUNT
users := make([]interface{}, count)
for i := 0; i < count; i++ {
loop_user := User{}
loop_user.Init()
loop_user.Email = fmt.Sprintf("report-%d#example.com", i)
users[i] = loop_user
}
bulk := uc.Bulk()
bulk.Unordered()
bulk.Insert(users...)
_, bulkErr := bulk.Run()
if bulkErr != nil {
panic(err)
}
}
}