Gorm Constraints

Foreign Key Constraint

GORM creates foreign key constraints for associations automatically. You can configure OnDelete and OnUpdate actions with the constraint tag:

type User struct {
    gorm.Model
    CompanyID  int
    Company    Company    `gorm:"constraint:OnUpdate:CASCADE,OnDelete:SET NULL;"`
    CreditCard CreditCard `gorm:"constraint:OnUpdate:CASCADE,OnDelete:SET NULL;"`
}

type CreditCard struct {
    gorm.Model
    Number string
    UserID uint
}

type Company struct {
    ID   int
    Name string
}

Available Actions

Disabling Foreign Key Constraints

To disable foreign key constraint creation during migration:

db, err := gorm.Open(sqlite.Open("gorm.db"), &gorm.Config{
    DisableForeignKeyConstraintWhenMigrating: true,
})

Use cases:

• Performance during bulk migrations
• Circular dependencies between tables
• Legacy databases without constraint support

When NOT to Use

• When application-level logic is preferred - If you need complex, multi-step validation, handle it in your service layer or hooks instead of database constraints.
• For temporary or staging data - Constraints can hinder the process of loading incomplete or intermediate data. Disable them during such operations.
• In a shared database with multiple applications - If other applications don't respect the constraints, it can lead to issues. Ensure all connected systems are aware.
• When database performance is paramount - Constraints add overhead to write operations. For high-throughput ingest systems, you might defer validation to a separate process.
• For databases that don't support them well - Not all databases (especially older versions or some NoSQL-like systems) have robust support for all constraint types.

Quick Reference

Reference

• Official Docs: https://gorm.io/docs/constraints.html