class ActiveRecord::SessionStore::Session

The default Active Record class.

def self.find_by_session_id(session_id) 

def self.find_by_session_id(session_id)
  find_by_sessid(session_id)
end

def self.find_by_session_id(session_id) 

def self.find_by_session_id(session_id)
  where(session_id: session_id).first
end

def data

Lazy-deserialize session state. 
def data
  @data ||= self.class.deserialize(read_attribute(@@data_column_name)) || {}
end

def data_column_size_limit 

def data_column_size_limit
  @data_column_size_limit ||= columns_hash[data_column_name].limit
end

def find_by_session_id(session_id)

Hook to set up sessid compatibility. 
def find_by_session_id(session_id)
  SEMAPHORE.synchronize { setup_sessid_compatibility! }
  find_by_session_id(session_id)
end

def initialize(*) 

def initialize(*)
  @data = nil
  super
end

def loaded?

Has the session been loaded yet? 
def loaded?
  @data
end

def raise_on_session_data_overflow!

ActionController::SessionOverflowError.
larger than the data storage column. Raises
Ensures that the data about to be stored in the database is not 
def raise_on_session_data_overflow!
  unless loaded?
    throw :abort
  end
  limit = self.class.data_column_size_limit
  if limit and read_attribute(@@data_column_name).size > limit
    raise ActionController::SessionOverflowError
  end
end

def secure!

when this is done.
on all existing sessions in the database. Users will not lose their session
To secure sessions created on those old versions, this method can be called
Sessions created on version <= 1.1.3 were guessable via a timing attack.
(see https://github.com/rack/rack/security/advisories/GHSA-hrqr-hxpp-chr3).
This method was introduced when addressing CVE-2019-16782 
def secure!
  session_id_column = if self.class.columns_hash['sessid']
    :sessid
  else
    :session_id
  end
  raw_session_id = read_attribute(session_id_column)
  if ActionDispatch::Session::ActiveRecordStore.private_session_id?(raw_session_id)
    # is already private, nothing to do
  else
    session_id_object = Rack::Session::SessionId.new(raw_session_id)
    update_column(session_id_column, session_id_object.private_id)
  end
end

def serialize_data! 

def serialize_data!
  unless loaded?
    throw :abort
  end
  write_attribute(@@data_column_name, self.class.serialize(data))
end

def session_id_column 

def session_id_column
  'session_id'
end

def setup_sessid_compatibility!

Compatibility with tables using sessid instead of session_id. 
def setup_sessid_compatibility!
  # Reset column info since it may be stale.
  reset_column_information
  if columns_hash['sessid']
    def self.find_by_session_id(session_id)
      find_by_sessid(session_id)
    end
    define_method(:session_id)  { sessid }
    define_method(:session_id=) { |session_id| self.sessid = session_id }
  else
    class << self; remove_possible_method :find_by_session_id; end
    def self.find_by_session_id(session_id)
      where(session_id: session_id).first
    end
  end
end