Script to automate database upgrades on Heroku

upgrade_heroku_db.sh

#!/bin/bash
set -e

app=$APP_NAME
old_db_env_var=$OLD_DB_ENV_VAR
new_db_env_var=$NEW_DB_ENV_VAR
remove_addon_name=$REMOVE_ADDON_NAME

old_db_url=`heroku config:get -a $app $OLD_DB_ENV_VAR`
new_db_url=`heroku config:get -a $app $new_db_env_var`
scale_in="web=0" # or "worker=0" or "web=0 worker=0" 
scale_out="web=1" # or "worker=1" or "web=1 worker=1"

# enable maintenance mode
heroku maintenance:on -a $app

# scale in
heroku ps:scale -a $app $scale_in

# begin migration
heroku pg:copy -a $app $old_db_url $new_db_env_var

# remove old addon
heroku addons:destroy -a $app --confirm $app $remove_addon_name

# update config
heroku config:set -a $app DATABASE_URL=$new_db_url

# scale out
heroku ps:scale -a $app $scale_out

# maintainence mode off
heroku maintenance:off -a $app