ruby on rails - 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 I wanted to set a default value:

def change
  change_column :contests, :prize, :integer, :default => 200

This works fine on my local machine, where I am using MySQL DB. However, when I push to my production site (which is hosted on Heroku, which gives me a Postgres DB) I get the following error:

PGError: ERROR:  column "prize" cannot be cast to type "pg_catalog.int4"
: ALTER TABLE "contests" ALTER COLUMN "prize" TYPE integer

In this article: http://www.postgresonline.com/periodical.php?i_id=3 they discuss the use of the USING to solve this problem. But I don't know how I can do that, and whether this is appropriate for what I'm trying to do.

Any insight into figuring this out would be very much appreciated.

Thanks! Ringo

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