Writes the migration to change all db string columns to text.

schema_string_changer.rb

module ActiveRecord
  class Schema
    def self.define(options, &block)
      instance_eval(&block)
    end
    
    def self.create_table(name, opts, &block)
      yield StringLogger.new name
    end
    def self.method_missing(method, *args, &block)
      # We don't care
    end
  end
  
  class StringLogger
    attr_accessor :table_name
    def initialize(table_name)
      @table_name = table_name
    end
    def string(name, opts={})
      puts "change_column :#{@table_name}, :#{name}, :text"
    end
    def method_missing(method, *args, &block)
      # We don't care
    end
  end
end

Would you just load this as a new initializer and then just run rake db:create ?

No, nothing fancy like that. This just knows enough to interpret the DSL in schema.rb the way we want. You would just cut and paste the schema at the end of the file (or load it) and then run it with plain Ruby.