How Does GORM's Upsert Feature Work Compared to FirstOrCreate and FirstOrInit?

Upsert: Creating or Updating in GORM

In GORM, both FirstOrCreate and FirstOrInit methods can be employed to retrieve or create a database record. However, determining whether a record was newly created or updated can be unclear.

Upsert Solution with Upsert-On-Conflict

From GORM 1.20.x onwards, an enhanced Upsert feature is introduced, which utilizes conflict handling capabilities for various databases.

// Update columns when conflict on id
DB.Clauses(clause.OnConflict{
  Columns:   []clause.Column{{Name: "id"}},
  DoUpdates: clause.AssignmentColumns([]string{"name", "age"}),
}).Create(&users)

This snippet translates to SQL statements such as:

• SQL Server: MERGE INTO "users" USING *** WHEN NOT MATCHED THEN INSERT *** WHEN MATCHED THEN UPDATE SET "name"="excluded"."name";
• PostgreSQL: INSERT INTO "users" *** ON CONFLICT ("id") DO UPDATE SET "name"="excluded"."name", "age"="excluded"."age";
• MySQL: INSERT INTO 'users' *** ON DUPLICATE KEY UPDATE 'name'=VALUES(name),'age=VALUES(age);

Fallback Solution for Older GORM Versions

For GORM versions prior to 1.9.x, a more efficient approach is to attempt an update first, followed by creating a new record if no match is found.

// Update only set name=nick
if err := db.Model(&newUser).Where("id = ?", 3333).Update("name", "nick").Error; err != nil {
  // Handle error...
  if gorm.IsRecordNotFoundError(err) {
    db.Create(&newUser)  // Create new record from newUser
  }
}

Distinguishing between FirstOrInit and FirstOrCreate

While both methods serve a similar purpose, their behavior is distinct:

• FirstOrInit: Initializes a struct if the record does not exist, but does not create the record.
• FirstOrCreate: Creates a record if it does not exist, and retrieves the record to the struct.

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