GORM update array of associations - postgresql

Question

I have an struct type Stat which has many-one associations with Score
type Stat struct {
gorm.Model
StatID string `json:"id" gorm:"uniqueIndex:idx_stat"`
Scores []Score `json:"scores"`
}
and Score is
type Score struct {
gorm.Model
Name string `json:"name" gorm:"uniqueIndex:idx_score"`
Score int `json:"score,string"`
ScoreStatID uint `json:"score_stat_id" gorm:"uniqueIndex:idx_score"`
}
A stat won't change so it has a unique constraint on its stat ID (different from its index key). However the associated scores may/will change with time. I am running a cron job to retrieve the latest scores for the stat objects.
What I would like my code to do is update the Score objects associated with a Stat object each time, rather than create new ones. I though that a uniqueIndex on the Score fields (as you can see above) would handle this, but to no avail.
My latest attempt is to do this
for _, v := range stats {
if err := db.Where("stat_id = ? ", v.StatID).First(&v).Error; errors.Is(err, gorm.ErrRecordNotFound) {
if err := db.Create(&v).Error; err != nil {
return err
}
continue
}
if err := db.Model(&v).Updates(Stat{Scores: v.Scores}).Error; err != nil {
fmt.Println("saving updated data failed", err)
}
}
i.e check/create the stat object and then attempt to update all the scores associated with it. However with these constraints I get the error
ERROR: duplicate key value violates unique constraint "idx_score" (SQLSTATE 23505)
So when I attempt to do this without the constraint, I get duplicated entries within the table.
How can I update or create the array of associations without creating duplicated records and in effect just updating the score values to the new ones (if they have changed)?
EDIT:
I thought I had it with the following code:
for _, v := range stats {
tmpScores := v.Scores
if err := db.Where("stat_id = ? ", v.ScoreID).Preload("Scores").First(&v).Error; errors.Is(err, gorm.ErrRecordNotFound) {
if err := db.Create(&v).Error; err != nil {
return err
}
continue
}
v.Scores = tmpScores
if err := db.Session(&gorm.Session{FullSaveAssociations: true}).Updates(&v).Error; err != nil {
fmt.Println("saving updated data failed", err)
}
}
however this isn't quite right. The issue is if I do it this way, then the v.Scores are the values from the database, not the updated ones, so I save the scores into tmpScores and then reset them however that doesn't work because now the associated ID isn't correct on the association and it creates new entries...