To copy database from one heroku app to another -
heroku pg:backups capture [database_name]
heroku pg:backups restore $(heroku pg:backups public-url --app source_app) DATABASE_URL --app target_app
You can refer to https://devcenter.heroku.com/articles/heroku-postgres-backups for more information.
To copy database from local to heroku -
Dump your local database in compressed format using the open source pg_dump tool: PGPASSWORD=mypassword pg_dump -Fc --no-acl --no-owner -h localhost -U myuser mydb > mydb.dump
where myuser
is your database username and mydb
is the database name.