Migrations

Version-controlled database schema changes with up/down functions.

Migrations let you evolve your database schema over time with version-controlled Go functions.

Creating a Migration

go run cmd/main.go make:migration create_posts_table
# Creates: database/migrations/YYYYMMDDHHMMSS_create_posts_table.go

Migration Structure

Each migration file registers itself in init():

package migrations

import "gorm.io/gorm"

func init() {
    Register(Migration{
        Version: "20260101120000_create_posts_table",
        Up: func(db *gorm.DB) error {
            type Post struct {
                ID        uint   `gorm:"primaryKey"`
                Title     string `gorm:"size:255;not null"`
                Body      string `gorm:"type:text"`
                UserID    uint
                CreatedAt time.Time
                UpdatedAt time.Time
                DeletedAt gorm.DeletedAt `gorm:"index"`
            }
            return db.AutoMigrate(&Post{})
        },
        Down: func(db *gorm.DB) error {
            return db.Migrator().DropTable("posts")
        },
    })
}

Running Migrations

# Apply all pending migrations
go run cmd/main.go migrate

# Rollback the last batch
go run cmd/main.go migrate:rollback

# Check migration status
go run cmd/main.go migrate:status

How It Works

• Migrations are tracked in a schema_migrations table with version, batch number, and timestamp
• Each migrate run applies all pending migrations in a new batch
• migrate:rollback undoes the last batch by running Down functions in reverse order
• migrate:status shows which migrations have been applied and which are pending