I'm using gorm with postgres in my Go app.
I want to create a new user in the database, but there is a good chance that that user will already exist. If so, I want to not do anything with the database, but I want know about it so I can tell the user.
The good news is, that's already what gorm.Create(..)
does. Trying to create a record with a duplicate unique key will return an error. There are two problems:
- I want better error messages. I want to write custom user-facing error messages that are different for "This email address already exists" than "There was an actual internal error." I don't know how to diferentiate between these two events other than trying to parse the error string returned by
Create()
which seems bug prone. - I don't want to clutter my logs. Calling
Create()
with an object that already exists logs an error message to stdout. I don't really consider this an "error" since I was expecting it to happen and I don't want to flood my logs with a bunch of these warnings.
I know I could use a transaction to first check for a user with the given id and then create them if one does not already exist, but it seems like there should be a simpler solution to such a basic thing. How are you supposed to do this?
I'm currently doing this:
func (self databaseWrapper) CreateUser(user *User) error {
db := self.db
db.NewRecord(*user)
err := db.Create(user).Error
if err != nil {
if db.Where(user.ID).Take(&User{}).Error == nil {
return fmt.Errorf("A user already exists with id %v", user.ID)
}
if db.Where(User{Email: user.Email}).Take(&User{}).Error == nil {
return fmt.Errorf("A user already exists with the given email address: %v", user.Email)
}
return fmt.Errorf("Error creating user")
}
return nil
}
Which is a little inefficient and gives the ugly output:
go test
(/home/quinn/workspace/aev/sensor/backend/server/database.go:125)
[2019-09-01 14:45:40] pq: duplicate key value violates unique constraint "users_pkey"
(/home/quinn/workspace/aev/sensor/backend/server/database.go:125)
[2019-09-01 14:45:40] pq: duplicate key value violates unique constraint "uix_users_email"
PASS
ok 3.215s
even when everything worked as expected.