status-go/protocol/migrations/sqlite/README.md

How to write migrations?

We only write up migrations, down migrations are not always possible in sqlite or too complex/too expensive. For example to remove a column you would have to duplicate the table, copy over the data, delete and recreated. This can be very expensive for some tables (user_messages for example), so should not be attempted.

Notes

One issue we faced multiple times is that updates to user_messages can be very expensive, leading to slow upgrade times and interrupted migrations. So avoid writes if not necessary.