Rails Migration

change-datetime-column.rb

class MillisecondsDateTime < ActiveRecord::Migration
  def up
    ActiveRecord::Base.connection.tables.each do |table|
      ActiveRecord::Base.connection.columns(table).each do |column|
        if column.type == :datetime
          change_column table, column.name, :datetime, limit: 6
          add_index table, column.name
        end
      end
    end
  end

  def down
    ActiveRecord::Base.connection.tables.each do |table|
      ActiveRecord::Base.connection.columns(table).each do |column|
        if column.type == :datetime
          change_column table, column.name, :datetime
          remove_index table, column.name
        end
      end
    end
  end
end