# File lib/rubyrep/table_scan.rb, line 44
    def initialize(session, left_table, right_table = nil)
      if session.left.primary_key_names(left_table).empty?
        raise "Table '#{left_table}' doesn't have a primary key. Cannot scan."
      end
      
      self.session, self.left_table, self.right_table = session, left_table, right_table
      self.right_table ||= self.left_table
      self.primary_key_names = session.left.primary_key_names left_table
    end