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The latest Heroku stack requires postgres and will not allow SQLite at all
( I think it is called Cedars ) When you deploy, you will want to deploy
on an older stack that allows SQLite. (I think Bamboo works with SQLite.)
If you can deploy with SQLite, then you should not have any
reconfigurations.

If you do end up having to deploy to postgres on Heroku you will have to
make sure your Gemfile, database.yml, and possibly other files are adjusted
to have SQLlite in the development environment and postgres in the
production environment. At that point, you may find that your app performs
differently in dev than production. If so, it is probably due to
underlying nuances/differences in the two databases. Heroku STRONGLY
recommends that you run postgres in your dev environment for just this
reason.