Создана ли таблица ar_internal_metadata на производстве?

Ответ 1

Это в основном переключатель безопасности, за счет усложнения и изменения развертывания приложений Rail:

Rails 5 has added a new table ar_internal_metadata
to store environment version which is used at the
time of migrating the database.

When the first time rake db:migrate is executed
then new table stores the value production. Now
whenever we load database schema or database
structure by running rake db:schema:load or
rake db:structure:load Rails will check if Rails
environment is "production" or not. If not then
Rails will raise an exception and thus
preventing the data wipeout.

http://blog.bigbinary.com/2016/06/07/rails-5-prevents-destructive-action-on-production-db.html