Is there something like sql.NullJson akin to sql.NullString in golang? - go

Question

I am querying from postgres using golang, one of the field contains json that can sometimes be NULL
Like this
row := db.QueryRow(
"select my_string, my_json from my_table where my_string = $1",
my_id)
var my_string sql.NullString
var myjson MyJsonStruct
err := row.Scan(&my_string2, &myjson)
But I am getting
sql: Scan error on column index 2, name "my_json": unsupported Scan, storing driver.Value type <nil> into type *main.MyJsonStruct
I checked https://godoc.org/database/sql but didn't find sql.NullJson What is a go way of dealing with this situation?

Answer 1

No, there is no sql.json. I think the best way to dealing with json column in db is to implement valuer and scanner. so something like this :
// Scan implements database/sql.Scanner interface
func (m *MyJsonStruct) Scan(src interface{}) error {
if src == nil {
return nil
}
data, ok := src.([]byte)
if !ok {
return errors.New("type assertion to []byte failed")
}
var myJsonStruct MyJsonStruct
if err := json.Unmarshal(data, &myJsonStruct); err != nil {
return fmt.Errorf("unmarshal myJsonStruct: %w", err)
}
*m = myJsonStruct
return nil
}
// Value implements database/sql/driver.Valuer interface
func (m MyJsonStruct) Value() (driver.Value, error) {
data, err := json.Marshal(m)
if err != nil {
return nil, fmt.Errorf("marshal myJsonStruct: %w", err)
}
return data, nil
}