Best Practices for Versioning Schemas with DbMouse
1. Use a linear, sequential migration strategy
Store migrations as ordered files (timestamp or incremental number prefixes) and apply them in a single forward sequence to avoid branching conflicts and ensure reproducible schema state.
2. Keep each migration small and focused
Make each migration perform a single logical change (e.g., add column, create table, modify index). Small migrations are easier to review, test, and rollback.
3. Include idempotent safety where possible
Write migrations so repeated application fails safely or no-ops (e.g., check for existence before creating/dropping). This reduces risk during re-runs in CI or recovery scenarios.
4. Track applied migrations in a dedicated table
Have DbMouse record applied migration identifiers and timestamps in a migrations table so deployments can detect which scripts ran and in what order.
5. Keep schema and data migrations separate
Avoid mixing large data transformations with structural changes; if you must, split into multiple migrations so schema changes can be deployed and verified independently of heavy data work.
6. Write reversible migrations or provide explicit rollbacks
When possible, include a rollback (down) script or a clear manual rollback plan to recover from bad deployments quickly.
7. Review and test migrations in staging with production-like data
Run migrations against a staging database that mirrors production schema and volume to uncover performance or locking issues before production deployment.
8. Use transactional migrations for safety
Wrap schema changes in transactions when the database supports transactional DDL so partial failures don’t leave the schema inconsistent.
9. Monitor and limit locking/long-running operations
Avoid operations that cause long table locks (e.g., large ALTER TABLEs); prefer online schema changes, chunked data migrations, or maintenance windows when needed.
10. Store migration scripts in version control alongside application code
Keep migrations in the same repo as the application to ensure schema changes are versioned with code and reviewed in pull requests.
11. Document intent and prerequisites in each migration
Add a brief header comment explaining why the change is needed, expected impact, and any manual steps required (e.g., backfill timing).
12. Automate applying migrations in CI/CD with governance
Run migration linting and dry-run checks in CI, and apply migrations through automated pipelines with safeguards (approvals, feature flags, canary deployments).
13. Use feature toggles to decouple deploy and release
When schema changes are incompatible with current code, deploy schema-first with feature flags so the new code path can be enabled safely later.
14. Clean up old/irrelevant migrations periodically (carefully)
After many versions, consider consolidating migration history into a baseline schema snapshot for faster setup, but only after ensuring all environments are consistent.
15. Backup before risky migrations
Take backups or ensure a reliable restore point before applying high-impact migrations so you can recover if something goes wrong.
If you want, I can convert these into a checklist, a CI pipeline snippet for applying DbMouse migrations, or example migration file templates.
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