After upgrading the rails code to <version>,
you must upgrade existing databases using these commands:

$ bundle exec rake db:migrate
$ bundle exec rake cartodb:db:load_functions
$ bundle exec rake cartodb:db:load_triggers
$ bundle exec rake cartodb:db:create_importer_schema
$ bundle exec rake cartodb:db:migrate_to[<version>]

NOTE: rails must be restarted after an upgrade