get_primary_key

# File activerecord/lib/active_record/attribute_methods/primary_key.rb, line 66
        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 && table_exists?
              connection.schema_cache.primary_keys[table_name]
            else
              'id'
            end
          end
        end