Rails: change column type, but keep data

Question

I have a model with a column of type integer which I want to convert to type string. Now I'm looking for the best way to change the column type without losing the data. Is there a painless way to accomplish this?

Answer 1

A standard migration using the change_column method will convert integers to strings without any data loss. rake db:rollback will also do the reverse migration without error if required.

Here is the test migration I used to confirm this behaviour:

class ChangeAgeToString < ActiveRecord::Migration   def self.up     change_column :users, :age, :string   end    def self.down     change_column :users, :age, :integer   end end 

Answer 2

for postgres in migration

 change_column :table_name, :field,'boolean USING (CASE field WHEN \'your any string as true\' THEN \'t\'::boolean ELSE \'f\'::boolean END)' 

and to any valid type similar