Migrate

---
name: migrate
description: "Run/create DB migrations (Alembic, Prisma, Laravel, Django, Flyway, Drizzle); checks backup. Triggers: apply migration, rollback, generate migration."
effort: medium
disable-model-invocation: true
argument-hint: "[direction]"
allowed-tools: Bash, Read
hooks:
  PreToolUse:
    - matcher: "Bash"
      hooks:
        - type: command
          command: "echo 'Reminder: ensure database backup exists before running migrations'"
scripts:
  - scripts/migration-status.py
---

# /migrate - Database Migration Workflow

$ARGUMENTS

## What This Command Does

Create, run, or manage database migrations with auto-detection of the migration tool.

## Project context

- Migration tools: !`ls alembic.ini prisma/ database/migrations/ manage.py 2>/dev/null`

## Migration Status Script

Detect migration tool and report status:
```bash
python3 scripts/migration-status.py [directory]
```

Returns JSON with: `tool`, `config_file`, `migrations_dir`, `total_migrations`, `latest`, `commands{}` (status/create/upgrade/downgrade).

## Auto-Detection

| File Found | Tool | Commands |
|------------|------|----------|
| `alembic.ini` | Alembic | `alembic revision`, `alembic upgrade` |
| `prisma/schema.prisma` | Prisma | `npx prisma migrate dev` |
| `database/migrations/` + `artisan` | Laravel | `php artisan migrate` |
| `manage.py` | Django | `python manage.py migrate` |
| `flyway.conf` | Flyway | `flyway migrate` |
| `drizzle.config.ts` | Drizzle | `npx drizzle-kit push` |

## Workflow

### Create New Migration
1. Detect migration tool
2. Generate migration from model/schema changes
3. Review generated SQL
4. Validate syntax

### Run Migrations
1. Show pending migrations
2. Dry-run if supported (`--pretend`, `--sql`)
3. Backup reminder
4. Apply with user confirmation
5. Verify success

### Rollback
1. Show last applied migration
2. Confirm rollback scope
3. Execute rollback
4. Verify state

## Safety Checks (MANDATORY)

- [ ] Migration tested on development/staging first
- [ ] Rollback path verified
- [ ] No data loss in forward or backward direction
- [ ] Large table operations use concurrent/online DDL
- [ ] Backup exists or reminder given

## Usage Examples

```
/migrate                     # Show migration status
/migrate create add_users    # Create new migration
/migrate run                 # Apply pending migrations
/migrate rollback            # Rollback last migration
/migrate status              # Show applied/pending migrations
```

## Reference Skill
Use `migration-patterns` skill for zero-downtime strategies and best practices.

## Rules

- **MUST** verify a recent backup exists (or confirmed in-progress) before any forward migration on production
- **MUST** show the generated SQL (dry-run / `--pretend` / `--sql`) before applying — the user approves the diff, not just the command
- **NEVER** run destructive migrations (DROP TABLE/COLUMN, NOT NULL on existing column, type change) without a tested rollback path
- **NEVER** mix schema changes and data backfill in the same migration — they fail differently and roll back differently
- **CRITICAL**: large-table operations use the concurrent/online variant (`ALTER TABLE ... ALGORITHM=INPLACE`, `CREATE INDEX CONCURRENTLY`) — table locks in production cause outages, not slowdowns
- **MANDATORY**: migrations test on a non-production environment first with representative data volume

## Gotchas

- `alembic upgrade head` silently skips migrations with `branches` if the branch head is not explicit. Multi-head migrations need `alembic upgrade <revision>@head` or a merge migration first.
- Prisma's `prisma migrate dev` auto-generates migrations AND applies them AND reseeds the dev database. Running it on a production-connected config destroys data. Always use `prisma migrate deploy` in non-dev.
- Laravel's `migrate` command without `--force` refuses to run in `APP_ENV=production`. Scripts that blindly run `migrate` hang on interactive prompts in prod — always use `artisan migrate --force` in automation.
- Django's `migrate --fake` marks a migration as applied **without running it**. Intended for manual data fixes, but accidentally using it skips real schema changes and silently diverges production from code.
- `CREATE INDEX CONCURRENTLY` (Postgres) cannot run inside a transaction. Alembic wraps each migration in a transaction by default — concurrent index creation needs `op.execute()` with `autocommit_block()` or a manual `COMMIT`.
- Rolling back a forward migration that added a NOT NULL column deletes the column; data in that column is gone. "Rollback" is not "undo" if the column held user data during the forward window.

## When NOT to Use

- For **zero-downtime schema evolution** strategy (expand-contract, double-write) — use `/migration-patterns`
- For designing the schema from scratch — use `/database-patterns`
- For application-layer rollback (deploying previous code) — use `/rollback`
- For CI-triggered migrations — use `/ci` or `/deploy`
- When no migration tool is detected — propose one from `/app-builder` instead of ad-hoc SQL