Allow specified session keys to be stored in a separate column using ActiveRecordStore. Useful for clearing sessions based on user_id.

native_columns_store.rb

class NativeColumnStore < ActiveRecord::SessionStore::Session
  class << self
    attr_reader :native_columns
    def native_columns=(columns)
      @native_columns = columns.map(&:to_s)
    end
    @native_columns = []
  end
 
  def data
    @data ||= begin
      unmarshaled_data = super
      self.class.native_columns.each do |column|
        unmarshaled_data.merge!(column => self[column]) if self[column].present?
      end
      unmarshaled_data
    end
  end
 
  private
 
  def marshal_data!
    return false unless loaded?
    self.class.native_columns.each do |column|
      self[column] = data[column]
    end
    marshalled_data = self.class.marshal(data.except(*self.class.native_columns))
    write_attribute(@@data_column_name, marshalled_data)
  end
end

native_columns_store_spec.rb

require 'spec_helper'
 
describe NativeColumnsStore do
  subject(:store) { NativeColumnsStore.new(session_id: '123') }
 
  before do
    NativeColumnsStore.native_columns = [:user_id]
    store.data[:test] = 'test_data'
    store.data[:user_id] = 3
    store.save!
    store.reload
  end
 
  it 'merges user_id into #data' do
    store.data[:user_id].should eq 3
  end
 
  it 'saves user_id in separate column' do
    store.user_id.should eq 3
  end
 
  it 'doesnt store user_id in marshaled data column' do
    marshaled_data = NativeColumnsStore.unmarshal(store.read_attribute(:data))
    marshaled_data.count.should eq 1
    marshaled_data.should have_key(:test)
  end
 
  after { NativeColumnsStore.native_columns = [] }
end

session_store.rb

SSOServer::Application.config.session_store :active_record_store
ActiveRecord::SessionStore.session_class = UserSession

user_session.rb

require 'native_columns_store'
 
class UserSession < NativeColumnsStore
  self.native_columns = [:user_id]
end

Cool. Thanks!

One more addition: store.data keeps keys as symbols. So, I changed native_columns setter to this:

def native_columns=(columns)
  @native_columns = columns.map(&:to_sym)
end