How to turn off 'on duplicate' statement with use foreign key in GORM?

When using GORM, handling ON DUPLICATE KEY UPDATE statements related to foreign keys typically involves managing duplicate data during record insertion. In database management, ON DUPLICATE KEY UPDATE is commonly used to update existing records instead of throwing errors when attempting to insert duplicate data.

GORM is a popular Go language ORM library for handling database operations, but it does not directly provide a method similar to SQL's ON DUPLICATE KEY UPDATE. However, we can use several strategies to achieve similar effects.

Method 1: Using Clauses with ON CONFLICT

If you are using PostgreSQL, you can use the ON CONFLICT statement to handle potential duplicate key issues. As follows:

go
import (
  "gorm.io/gorm"
)

func UpsertWithOnConflict(db *gorm.DB, user *User) error {
  return db.Clauses(clause.OnConflict{
    Columns:   []clause.Column{{Name: "email"}}, // Assuming email is the foreign key
    DoUpdates: clause.Assignments(map[string]interface{}{"name": user.Name, "age": user.Age}),
  }).Create(user).Error
}

Here, ON CONFLICT is defined for the email column. If the data being inserted conflicts with existing data on the email foreign key, it updates the name and age fields of the record.

Method 2: Query First, Then Decide Insert or Update

If your database or GORM version does not support ON CONFLICT, you can handle it by first querying and then deciding whether to insert or update:

go
func InsertOrUpdate(db *gorm.DB, user *User) error {
  var existingUser User
  // Assuming email is used as the search condition
  result := db.Where("email = ?", user.Email).First(&existingUser)

  if result.Error == gorm.ErrRecordNotFound {
    // Not found, perform insert operation
    return db.Create(user).Error
  } else if result.Error != nil {
    return result.Error
  }

  // Found, perform update operation
  return db.Model(&existingUser).Updates(user).Error
}

Method 3: Using Save Method

The Save method in GORM automatically chooses to update or insert based on the primary key. If the primary key is not set, it inserts a new record. If the primary key is set, it updates the existing record.

go
func SaveUser(db *gorm.DB, user *User) error {
  return db.Save(user).Error
}

This method is simple, but note that it updates all fields. If you only want to update specific fields, you may still need to use Method 2.

Summary

Although GORM does not directly provide the ON DUPLICATE KEY UPDATE functionality, similar effects can be achieved using ON CONFLICT, conditional queries to decide between insert and update, or the Save method. The specific method to use depends on your requirements and the database type (e.g., MySQL, PostgreSQL).