How to get RowsAffected in Go-Gorm's Association Mode - mysql

Question

I insert a relation by the following code:
db.Where(exercise).FirstOrCreate(&exercise).Model(&User{ID: userID}).Association("Exercises").Append(&exercise)
Corresponding SQL printed by debug console to the code is:
INSERT INTO `user_exercise` (`user_id`,`exercise_id`) SELECT 1,1 FROM DUAL WHERE NOT EXISTS (SELECT * FROM `user_exercise` WHERE `user_id` = 1 AND `exercise_id` = 1)
I want know if there are new record created in user_exercise, but due to the generated SQL, if a relation in user_exercise already exists, it won't insert and produce no error.
Go-Gorm's Association object doesn't have a RowsAffected attribute, so I can't get RowsAffected from the query to confirm if a new record is created.
Though I can get RowsAffected from the first db object, like
db.Where(exercise).FirstOrCreate(&exercise).Model(&User{ID: userID}).Association("Exercises").Append(&exercise)
if db.RowsAffected == 1 {
// do something
}
I wonder since the db is shared by all queries, if another query executed at the same time and affected rows > 0, is it safe to get RowsAffected from the global db object?

Answer 1

Assuming that the user_execise table has an unique constraint (user_id, exercise_id) the insert should return an error if you try to do it to an already created record. (Exactly what you want)
So just do something like this...
db.Where(exercise).FirstOrCreate(&exercise)
ue := struct {
UserID uint
ExerciseID uint
}{
UserID: userID,
ExerciseID exercise.ID
}
if err := db.Table("user_exercise").Create(&ue).Error; err != nil {
// will enter here if it wasn't created
}
If it doesn't returns an Error means that a new record was created