heroku + ActiveRecord 地雷

After `heroku rake db:migrate` is run,
we need to remember to run `heroku restart`,
or we might end up with database column
which is supposed to be an Integer (Fixnum)
is actually a String.

I was so nervous when I saw "0" + 1
and other mysterious things...
(e.g. someone says the column is there
but another one says it's not there...)

Not really a fault of anyone I guess..
but just remember to restart the servers.