Rails migrations - change_column with type conversion

Question

I already google\'d aroung a little bit and seems there\'s no satisfying answer for my problem.

I have a table with column of type string. I\'d like to run following

Answer 1

Not all databases allow changing of column type, the generally taken approach is to add a new column of the desired type, bring any data across, remove the old column and rename the new one.

add_column :users, :smoking_tmp, :boolean

User.reset_column_information # make the new column available to model methods
User.all.each do |user|
  user.smoking_tmp = user.smoking == 1 ? true : false # If smoking was an int, for example
  user.save
end

# OR as an update all call, set a default of false on the new column then update all to true if appropriate.
User.where(:smoking => 1).update_all(:smoking_tmp = true) 

remove_column :users, :smoking
rename_column :users, :smoking_tmp, :smoking