# Upgrading JupyterHub and its databases

## Definitions
db type: sqlite, postgres, mysql, others???
db fields: individual fields in a database table

## Basic use cases
- [ ] Simple upgrade - no database fields changed; no db type change
- [ ] Field changes  - database fields added, deleted or changed by a new JHub release/functionality; no db type change

## More complex use cases
- [ ] Field changes - database fields added, deleted or changed by user; no db type change
- [ ] db type change (i.e. sqlite to postgres) - fields may or may not change; db type does change

## Process
- Remind admins to back up Hub databases
- Possibly remind admins to make sure single user notebook data is saved/backed up
- Admin notify users (if desired) of planned upgrade

**Multi-step upgrade vs all at once**??
- Migrate database type (Hub at same release level) user-initiated
- Add/change/delete fields (Hub at same release level) user-initiated
- Add/change/delete files (Hub initiated - in prep for JHub release upgrade)
- Upgrade Hub to 0.7 after

- Upgrade/changes to: CHP, authenticators, spawners

## Other topics
- limitations of sqlite upgrade
- upgrade hub first or upgrade db first???

## Tools
- alembic
- scripts
- sqlalchemy?
- db tools