migration-check

/migration-check

Analyze database migrations for risks before running them.

Step 1: Environment Check

# Verify environment
echo "Environment: $NODE_ENV"
echo "Database: $DATABASE_URL"

⚠️ If this is production, proceed with extra caution.

Step 2: Check Pending Migrations

# Laravel
php artisan migrate:status

# Rails
rails db:migrate:status

# Prisma
npx prisma migrate status

# Knex
npx knex migrate:status

Step 3: Analyze Each Migration

For each pending migration, I'll assess:

Check	What I Look For
Destructive DDL	DROP TABLE, DROP COLUMN, TRUNCATE
Data modifications	DELETE, UPDATE affecting existing data
Constraint changes	Adding NOT NULL to populated columns
Index changes	Dropping indexes, adding unique constraints
Foreign keys	CASCADE DELETE risks

Risk Classification

• CRITICAL: Will delete/modify existing data
• HIGH: May fail or lock tables
• MEDIUM: Adds constraints, may need backfill
• LOW: Safe additive changes (CREATE, ADD COLUMN nullable)

Step 4: Check Existing Data

Before migrations that DROP or modify:

-- Check row counts in affected tables
SELECT 'users' as table_name, COUNT(*) as rows FROM users
UNION ALL
SELECT 'orders', COUNT(*) FROM orders;

-- Check if column being dropped has data
SELECT COUNT(*) FROM users WHERE deprecated_column IS NOT NULL;

Step 5: Pre-Migration Backup

Required for CRITICAL/HIGH risk migrations:

# Full database backup
pg_dump -Fc database_name > backup_pre_migration_$(date +%Y%m%d_%H%M%S).dump

# Single table backup
pg_dump -t affected_table database_name > table_backup.sql

Step 6: Migration Decision

I'll present:

## Migration Risk Assessment

### Migration: 2024_01_15_drop_legacy_users
**Risk Level:** CRITICAL
**Action:** DROP TABLE legacy_users
**Data at Risk:** 1,247 records

**Recommendation:**
1. Create backup: `pg_dump -t legacy_users db > legacy_users_backup.sql`
2. Verify these records are not needed
3. Proceed only after confirmation

### Migration: 2024_01_16_add_email_index
**Risk Level:** LOW
**Action:** ADD INDEX on email column
**Data at Risk:** None

**Recommendation:** Safe to proceed