IDs of child table is invalid when update in MySQL

[isutare412]

Explain your user case and expected results

❯ GORM_DIALECT=mysql go test
2025/06/05 22:53:08 testing mysql...

2025/06/05 22:53:08 /Users/redacted/gorm-issue-report/main_test.go:21
[1.735ms] [rows:1] INSERT INTO `envs` (`app_id`,`key`,`value`) VALUES (1,'KEY1','value1') ON DUPLICATE KEY UPDATE `app_id`=VALUES(`app_id`)

2025/06/05 22:53:08 /Users/redacted/gorm-issue-report/main_test.go:21
[6.075ms] [rows:1] INSERT INTO `apps` (`name`) VALUES ('foo')

2025/06/05 22:53:08 /Users/redacted/gorm-issue-report/main_test.go:35
[1.140ms] [rows:3] INSERT INTO `envs` (`app_id`,`key`,`value`) VALUES (1,'KEY1','value1-updated'),(1,'KEY2','value2-added') ON DUPLICATE KEY UPDATE `app_id`=VALUES(`app_id`),`key`=VALUES(`key`),`value`=VALUES(`value`)

2025/06/05 22:53:08 /Users/redacted/gorm-issue-report/main_test.go:35
[4.826ms] [rows:0] UPDATE `apps` SET `name`='foo' WHERE `id` = 1

2025/06/05 22:53:08 /Users/redacted/gorm-issue-report/main_test.go:42
[0.941ms] [rows:2] SELECT * FROM `envs` WHERE `envs`.`app_id` = 1

2025/06/05 22:53:08 /Users/redacted/gorm-issue-report/main_test.go:42
[2.121ms] [rows:1] SELECT * FROM `apps` WHERE `apps`.`id` = 1 ORDER BY `apps`.`id` LIMIT 1
--- FAIL: TestGORM (0.01s)
    main_test.go:22: appInitial: &{ID:1 Name:foo Envs:[0x1400037b2f0]}
    main_test.go:24:   env[0]: &{ID:1 AppID:1 Key:KEY1 Value:value1}
    main_test.go:36: appUpdated: &{ID:1 Name:foo Envs:[0x140002a3e90 0x140002a3ec0]}
    main_test.go:38:   env[0]: &{ID:2 AppID:1 Key:KEY1 Value:value1-updated}
    main_test.go:38:   env[1]: &{ID:3 AppID:1 Key:KEY2 Value:value2-added}
    main_test.go:43: appFetched: &{ID:1 Name:foo Envs:[0x140002f28a0 0x140002f2930]}
    main_test.go:45:   env[0]: &{ID:1 AppID:1 Key:KEY1 Value:value1-updated}
    main_test.go:45:   env[1]: &{ID:2 AppID:1 Key:KEY2 Value:value2-added}
    main_test.go:59: Expected env ID 1, got 2
    main_test.go:59: Expected env ID 2, got 3
FAIL
exit status 1
FAIL	gorm.io/playground	1.132s

Environment

• MySQL

Symptom

IDs after Update() is not same as those saved in database.
As you see, IDs in database is 1, 2 but IDs of updated results are 2, 3.

appUpdated: &{ID:1 Name:foo Envs:[0x140002a3e90 0x140002a3ec0]}
  env[0]: &{ID:2 AppID:1 Key:KEY1 Value:value1-updated}
  env[1]: &{ID:3 AppID:1 Key:KEY2 Value:value2-added}
appFetched: &{ID:1 Name:foo Envs:[0x140002f28a0 0x140002f2930]}
  env[0]: &{ID:1 AppID:1 Key:KEY1 Value:value1-updated}
  env[1]: &{ID:2 AppID:1 Key:KEY2 Value:value2-added}