Rails Migration to add a default value to created_at and updated_at so COPY_FROM can work

migration.rb

class ChangeRawDiagnosesCreatedAtAndUpdatedAt < ActiveRecord::Migration[5.1]
  def change
    change_column_default :raw_diagnoses, :created_at, from: nil, to: -> { 'CURRENT_TIMESTAMP' }
    change_column_default :raw_diagnoses, :updated_at, from: nil, to: -> { 'CURRENT_TIMESTAMP' }
  end
end