rake db：migrate如何在Heroku上工作？

Question

My app just crashed after I pushed to Heroku and ran rake db:migrate . But the error didn't make sense...

ActionView::Template::Error (undefined method `email_address' for #<Invite:0x000000065fb788>):

...because the migration contained:

rename_column :invites, :email, :email_address

So I eventually figured out that it worked after an app restart ( heroku restart ). Good deal.

However, I'm confused about how rake db:migrate works now. Every single other migration picked up the corresponding model attribute without the restart.

What happens when I run rake db:migrate on Heroku? What spurs the app to pickup the new model attributes and why didn't it work this time?

Answer 1

In a new rails app you can see the following

.../config/environments/development.rb

# In the development environment your application's code is reloaded on
# every request.  This slows down response time but is perfect for development
# since you don't have to restart the web server when you make code changes.
config.cache_classes = false

.../config/environments/production.rb

# Code is not reloaded between requests
config.cache_classes = true