get_primary_key

# File activerecord/lib/active_record/attribute_methods/primary_key.rb, line 32
        def get_primary_key(base_name) #:nodoc:
          return 'id' unless base_name && !base_name.blank?

          case primary_key_prefix_type
          when :table_name
            base_name.foreign_key(false)
          when :table_name_with_underscore
            base_name.foreign_key
          else
            if ActiveRecord::Base != self && connection.table_exists?(table_name)
              connection.primary_key(table_name)
            else
              'id'
            end
          end
        end