RoR: Cannot change_column in postgres, fine in MySQL (MySQL for development, Postgres on Heroku)

Question

I had a column called \"prize\":

create_table :contests do |t|
  t.text :prize

I recently realized that this will always be an integer and

Answer 1

First you should use the same DB in both environments to prevent this kind of surprises.

To run raw sql in migrations see this example http://guides.rubyonrails.org/migrations.html#using-the-up-down-methods

Answer 2

I think you'll have to do it by hand:

def up
    connection.execute(%q{
        alter table contests
        alter column prize type integer using cast(prize as integer),
        alter column price set default 200
    })
end

If you want to run the same migration in both MySQL and PostgreSQL then:

def up
    case ActiveRecord::Base.connection
    when ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
        connection.execute(%q{
            alter table contests
            alter column prize type integer using cast(prize as integer),
            alter column price set default 200
        })
    when ActiveRecord::ConnectionAdapters::MySQLAdapter
        # MySQL version...
    end
end

Once you get around this problem, your next task will be to switch your development environment over to PostgreSQL so that you can start fixing all the other little problems (such as GROUP BY issues, case sensitive LIKE, column truncation behavior, ...) that you'll run into.