How to insert multiple data at once

For Postgres lib pq supports bulk inserts: https://godoc.org/github.com/lib/pq#hdr-Bulk_imports

But same can be achieved through below code but where it is really helpful is when one tries to perform bulk conditional update (change the query accordingly).

For performing similar bulk inserts for Postgres, you can use the following function.

// ReplaceSQL replaces the instance occurrence of any string pattern with an increasing $n based sequence
func ReplaceSQL(old, searchPattern string) string {
   tmpCount := strings.Count(old, searchPattern)
   for m := 1; m <= tmpCount; m++ {
      old = strings.Replace(old, searchPattern, "$"+strconv.Itoa(m), 1)
   }
   return old
}

So above sample becomes

sqlStr := "INSERT INTO test(n1, n2, n3) VALUES "
vals := []interface{}{}

for _, row := range data {
   sqlStr += "(?, ?, ?),"
   vals = append(vals, row["v1"], row["v2"], row["v3"])
}

//trim the last ,
sqlStr = strings.TrimSuffix(sqlStr, ",")

//Replacing ? with $n for postgres
sqlStr = ReplaceSQL(sqlStr, "?")

//prepare the statement
stmt, _ := db.Prepare(sqlStr)

//format all vals at once
res, _ := stmt.Exec(vals...)

If you enable multi statements , then you can execute multiple statement at once. With that , you should be able to handle multiple inserts.

https://github.com/go-sql-driver/mysql#multistatements

Gorm V2 (released on 30th August 2020) now supports batch insert query.

// Pass slice data to method Create, GORM will generate a single SQL statement
// to insert all the data and backfill primary key values,
// hook methods will be invoked too.

var users = []User{{Name: "jinzhu1"}, {Name: "jinzhu2"}, {Name: "jinzhu3"}}
DB.Create(&users)

for _, user := range users {
  user.ID // 1,2,3
}

For more details refer to the official documentation here: https://gorm.io/docs/create.html.

why not something like this? (writing here without testing so there might be syntax errors):

sqlStr := "INSERT INTO test(n1, n2, n3) VALUES "
vals := []interface{}{}

for _, row := range data {
    sqlStr += "(?, ?, ?),"
    vals = append(vals, row["v1"], row["v2"], row["v3"])
}
//trim the last ,
sqlStr = sqlStr[0:len(sqlStr)-1]
//prepare the statement
stmt, _ := db.Prepare(sqlStr)

//format all vals at once
res, _ := stmt.Exec(vals...)