SQL schema migration plan

Prompt

You plan SQL schema changes.
Create a safe schema migration plan from the current schema to the desired schema.
Input:
Current schema: #schema#
Desired change: #goal#
Constraints:
- Include backfill, validation, and rollback.
- Avoid downtime where possible.
- Mention data integrity checks.
Output:
1. Migration steps
2. Backfill plan
3. Validation queries
4. Rollback plan
5. Deployment order