Rails Migrate Command

Execute database migrations with safety checks and production awareness.

Usage

/rails:migrate [action]

Actions

• (no argument) - Run pending migrations
• status - Show migration status
• rollback - Rollback last migration
• redo - Rollback and re-run last migration
• up VERSION=xxx - Run specific migration up
• down VERSION=xxx - Run specific migration down

Safety Checks

Before running migrations, verify:

1. Pending migrations exist

   bin/rails db:migrate:status
   

2. Review migration content

   • Check for potentially dangerous operations:
     • remove_column without ignored_columns
     • change_column on large tables
     • Non-concurrent index creation
     • add_column with null: false without default

3. Check for irreversible migrations

   • change_column without explicit up/down
   • Data migrations that can't be undone

Production Warnings

Flag these patterns with warnings:

Table Locks

# WARNING: May lock table
add_index :large_table, :column  # Should use algorithm: :concurrently
change_column :table, :column, :new_type  # May rewrite table

Data Loss

# WARNING: Irreversible
remove_column :orders, :status  # Check ignored_columns first
drop_table :old_table  # Ensure data is backed up

Long-Running

# WARNING: May take long time
add_column :users, :field, default: "value"  # On large tables
# Rails 7+ handles this efficiently, but warn for older Rails

Process

1. Show migration status
2. List pending migrations with summaries
3. Analyze each migration for safety concerns
4. If concerns found, display warnings
5. Run migrations (or ask for confirmation if concerns)
6. Show results and new schema state

Rollback Safety

Before rollback:

1. Check if migration is reversible
2. Warn about data that may be lost
3. Suggest alternatives if destructive

Output

Migration Status:
  up     20231201120000  Create users
  up     20231202130000  Add email to users
  down   20231203140000  Add orders table (pending)

Pending Migrations:
  20231203140000_add_orders_table.rb
    - Creates orders table
    - Adds foreign key to users
    - Adds index on user_id

Safety Check: ✓ No concerns found

Running migrations...
  == 20231203140000 AddOrdersTable: migrating ===
  -- create_table(:orders)
  -- add_index(:orders, :user_id)
  == 20231203140000 AddOrdersTable: migrated (0.0123s) ===

✓ Migration complete