Gorm AutoMigrate not updating existing Foreign Key with OnDelete constraint

Description

type Parent struct {
    ParentID          uuid.UUID `gorm:"type:uuid;primary_key;" json:"parentId,omitempty"`
    Name   string    `gorm:"type:varchar(255)" json:"name"`
}


type Child struct {
    ChildID     uuid.UUID      `gorm:"type:uuid;primary_key;" json:"childId"`
    Name   string    `gorm:"type:varchar(255)" json:"name"`

    // Foreign Key
    Parent Parent `gorm:"foreignkey:ParentID;constraint:OnDelete:CASCADE;"`
}

main.go:

func main() {
        . . .
    // Auto Migrate
    //
    db.AutoMigrate(
        &models.Parent{},
        &models.Child{},
    )

The existing model contained the FK relation already defined/applied to the DB. When I added the constraint to cascade DELETE (constraint:OnDelete:CASCADE;) and started up the server, I don't see this as having been applied.

Is this by design, or is this a bug? I found the following issue (#4110) which added support for migrating unique constraints. Perhaps OnDelete/OnUpdate require such a fix as well?

Comment From: github-actions[bot]

The issue has been automatically marked as stale as it missing playground pull request link, which is important to help others understand your issue effectively and make sure the issue hasn't been fixed on latest master, checkout https://github.com/go-gorm/playground for details. it will be closed in 30 days if no further activity occurs. if you are asking question, please use the Question template, most likely your question already answered https://github.com/go-gorm/gorm/issues or described in the document https://gorm.io ✨ Search Before Asking ✨

Comment From: a631807682

What dose I don't see this as having been applied means? I can not find the difference from the test, can you describe it? https://github.com/go-gorm/gorm/blob/master/tests/associations_test.go#L128

Comment From: Avinodh

@a631807682 - In the test you linked, the table is Dropped and then AutoMigrate() is called:

    DB.Migrator().DropTable(&Profile{}, &Member{})

    if err := DB.AutoMigrate(&Profile{}, &Member{}); err != nil {
        t.Fatalf("Failed to migrate, got error: %v", err)
    }

The issue I mention relates to an existing table on which a foreign key has already been defined. I am now trying to add on a 'constraint:OnDelete:CASCADE;' annotation to the model, but it is a no-op. The only way I could get the AutoMigration() to modify the FK on the table to cascade the delete was by manually dropping the the FK from the table, and having AutoMigrate() re-create it.

It doesn't seem like AutoMigrate can do this currently without requiring manually dropping the FK first.

Comment From: a631807682

It sounds like MigrateColumn problem, I'll check it later

Comment From: github-actions[bot]

The issue has been automatically marked as stale as it missing playground pull request link, which is important to help others understand your issue effectively and make sure the issue hasn't been fixed on latest master, checkout https://github.com/go-gorm/playground for details. it will be closed in 30 days if no further activity occurs. if you are asking question, please use the Question template, most likely your question already answered https://github.com/go-gorm/gorm/issues or described in the document https://gorm.io ✨ Search Before Asking ✨

Comment From: a631807682

Patch Constraint is not currently supported, and Constraint changes do not seem to take effect

https://github.com/go-gorm/gorm/blob/master/migrator/migrator.go#L133

Comment From: Avinodh

Thanks @a631807682 , that is unfortunate. Hopefully a fix for this can be prioritized soon.

Comment From: andig

@Avinodh I've just stumbled about the same problem:

type Device struct {
    ID      int `gorm:"primarykey"`
    Class   Class
    Type    string
    Details []DeviceDetail `gorm:"constraint:OnUpdate:CASCADE,OnDelete:CASCADE"`
}

type DeviceDetail struct {
    DeviceID int    `gorm:"primarykey"`
    Key      string `gorm:"primarykey"`
    Value    string
}

Any fix in sight?

Comment From: rootgrandfather

same

Comment From: bkmeneguello

This issue happens because the Migrator only checks if the constraint is present by the name, and not by its content: https://github.com/go-gorm/gorm/blob/418ee3fc1939d87a05bbb8ac6d7c7223e2c4571f/migrator/migrator.go#L166 Probably a method MigrateConstraint is necessary to check the definition and update accordingly.

Comment From: a631807682

https://github.com/go-gorm/gorm/issues/6381#issuecomment-1929427042