heroku run "POOL_SIZE=2 mix ecto.migrate"
see Deploying on Heroku — Phoenix v1.8.8
the DB will be empty - you should have some UI/backend to insert data.. or some kind of seed task if needed..
if not you can use something like Postico (mac) Postico 2 - or similar for your platform..
you could also dump your local DB and restore the heroku DB to that dump Importing and Exporting Heroku Postgres Databases | Heroku Dev Center
