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

If your strings in smoking column are already valid boolean values, the following statement will change the column type without losing data:

change_column :users, :smoking, 'boolean USING CAST(smoking AS boolean)'

Similarly, you can use this statement to cast columns to integer:

change_column :table_name, :column_name, 'integer USING CAST(column_name AS integer)'

I am using Postgres. Not sure whether this solution works for other databases.