Active Record Session Store

A session store backed by an Active Record class. A default class is provided, but any object duck-typing to an Active Record Session class with text session_id and data attributes is sufficient.

The default assumes a sessions tables with columns:

+id+ (numeric primary key),
+session_id+ (text, or longtext if your session data exceeds 65K), and
+data+ (text or longtext; careful if your session data exceeds 65KB).

The session_id column should always be indexed for speedy lookups. Session data is marshaled to the data column in Base64 format. If the data you write is larger than the column’s size limit, ActionController::SessionOverflowError will be raised.

You may configure the table name, primary key, and data column. For example, at the end of config/application.rb:

ActiveRecord::SessionStore::Session.table_name = 'legacy_session_table'
ActiveRecord::SessionStore::Session.primary_key = 'session_id'
ActiveRecord::SessionStore::Session.data_column_name = 'legacy_session_data'

Note that setting the primary key to the session_id frees you from having a separate id column if you don’t want it. However, you must set session.model.id = session.session_id by hand! A before filter on ApplicationController is a good place.

Since the default class is a simple Active Record, you get timestamps for free if you add created_at and updated_at datetime columns to the sessions table, making periodic session expiration a snap.

You may provide your own session class implementation, whether a feature-packed Active Record or a bare-metal high-performance SQL store, by setting

ActiveRecord::SessionStore.session_class = MySessionClass

You must implement these methods:

self.find_by_session_id(session_id)
initialize(hash_of_session_id_and_data, options_hash = {})
attr_reader :session_id
attr_accessor :data
save
destroy

The example SqlBypass class is a generic SQL session store. You may use it as a basis for high-performance database-specific stores.