How to cascade a DELETE in GORM?

To implement Cascade Delete in GORM, first ensure that the association relationships between your models are correctly configured. GORM uses the struct tags of the models to define these relationships. Cascade Delete is typically used to handle parent-child relationship data, ensuring that related child records are automatically deleted when the parent record is removed.

First, I will demonstrate how to set up the model relationships, then explain how to enable Cascade Delete.

Step 1: Setting Up Model Relationships

Assume we have two models, User and Profile. A user (User) can have one profile (Profile).

go
type User struct {
    gorm.Model
    Name    string
    Profile Profile 
}

type Profile struct {
    gorm.Model
    UserID uint
    Bio    string
}

In GORM, to establish a one-to-one relationship, include Profile as a field in the User model and use UserID as the foreign key in Profile.

Step 2: Configuring Cascade Delete

Next, we need to configure Cascade Delete. This can be achieved by setting the OnDelete constraint on the foreign key. In the Profile model, we can set it as follows:

go
type Profile struct {
    gorm.Model
    UserID uint `gorm:"constraint:OnDelete:CASCADE;"`
    Bio    string
}

Here, constraint:OnDelete:CASCADE specifies that when the associated User is deleted, the Profile should also be cascade deleted.

Step 3: Executing Delete Operations with GORM

Now that the relationships and cascade rules are set, we can simply delete a User, and the related Profile will be automatically deleted.

go
db := gorm.Open(...)
defer db.Close()

// Assume we want to delete the user with ID 1
var user User
db.First(&user, 1)
db.Delete(&user)

In the above code, after deleting the user with ID 1, the associated Profile will also be automatically deleted due to the cascade delete constraint.

Summary

Implementing Cascade Delete in GORM involves several key steps: correctly configuring the model relationships, setting the cascade delete constraints, and executing the delete operation through GORM. Through these steps, we can ensure data integrity and consistency, preventing orphaned child records. In production environments, this operation should be performed with caution, as delete operations are irreversible.