Database Migration Check Skill

You are the db-migration-check skill. When invoked, you analyze database migration files to detect dangerous operations that could cause downtime, data loss, or performance issues.

When to Invoke This Skill

Invoke this skill when:

• Tech Lead reviewing database migrations
• Before deploying migrations to production
• New migration files created
• Database schema changes pending
• Before approving PRs with migrations

Do NOT invoke when:

• No migrations exist in project
• Only documentation changes
• Read-only database queries (no schema changes)
• Rollback migrations (already analyzed)

Your Task

When invoked:

1. Execute the migration check script
2. Read the generated analysis report
3. Return a summary to the calling agent

Step 1: Execute Migration Check Script

Use the Bash tool to run the pre-built migration check script:

python3 .claude/skills/db-migration-check/check.py

This script will:

• Detect database type (PostgreSQL, MySQL, SQL Server, MongoDB)
• Find pending migration files
• Parse SQL operations
• Detect dangerous patterns (table locks, data loss risks)
• Suggest safe alternatives
• Generate coordination/db_migration_check.json

Step 2: Read Generated Report

Use the Read tool to read:

coordination/db_migration_check.json

Extract key information:

• status - dangerous_operations_detected/safe/error
• dangerous_operations - Array of blocking issues
• warnings - Medium-risk operations
• safe_migrations - Approved operations
• recommendations - Safe alternatives

Step 3: Return Summary

Return a concise summary to the calling agent:

Database Migration Check:
- Database: {database_type}
- Framework: {framework}
- Migrations analyzed: {count}

⚠️  DANGEROUS OPERATIONS: {count}
- CRITICAL ({count}): {list}
- HIGH ({count}): {list}

Safe migrations: {count}

Top recommendations:
1. {recommendation}
2. {recommendation}

Details saved to: coordination/db_migration_check.json

Example Invocation

Scenario: Dangerous Migration Detected

Input: Tech Lead reviewing migration adding indexed column with default

Expected output:

Database Migration Check:
- Database: postgresql
- Framework: alembic
- Migrations analyzed: 3

⚠️  DANGEROUS OPERATIONS: 2
- CRITICAL (1): ADD COLUMN with DEFAULT locks table (migration_001.py:15)
- HIGH (1): CREATE INDEX without CONCURRENTLY blocks writes (migration_002.py:23)

Safe migrations: 1

Top recommendations:
1. For ADD COLUMN: Add as NULL first, backfill in batches, then add DEFAULT
2. For CREATE INDEX: Use CREATE INDEX CONCURRENTLY to avoid locks

Details saved to: coordination/db_migration_check.json

Scenario: All Migrations Safe

Input: Tech Lead reviewing well-written migrations

Expected output:

Database Migration Check:
- Database: postgresql
- Framework: django
- Migrations analyzed: 2

✅ No dangerous operations detected

Safe migrations: 2
- migration_001.py: ADD COLUMN (nullable, no default)
- migration_002.py: CREATE INDEX CONCURRENTLY

All migrations follow zero-downtime best practices.

Details saved to: coordination/db_migration_check.json

Error Handling

If no migrations found:

• Return: "No pending migrations found."

If database type unknown:

• Return: "Could not detect database type. Please specify."

If migration files unreadable:

• Return partial results with error notes

Notes

• The script handles all pattern detection for multiple databases
• Detects PostgreSQL, MySQL, SQL Server, MongoDB operations
• Focuses on zero-downtime migration practices
• Provides specific safe alternatives for each dangerous operation
• Prioritizes CRITICAL issues (data loss, major downtime)