stop redifining methods on every call to set_primary_key

activerecord/lib/active_record/attribute_methods/primary_key.rb

@@ -14,11 +14,13 @@ module ClassMethods
         # Defines the primary key field -- can be overridden in subclasses. Overwriting will negate any effect of the
         # primary_key_prefix_type setting, though.
         def primary_key
-          reset_primary_key
+          @primary_key ||= reset_primary_key
         end
 
         def reset_primary_key #:nodoc:
-          key = get_primary_key(base_class.name)
+          key = self == base_class ? get_primary_key(base_class.name) :
+            base_class.primary_key
+
           set_primary_key(key)
           key
         end
@@ -40,6 +42,9 @@ def get_primary_key(base_name) #:nodoc:
           end
         end
 
+        attr_accessor :original_primary_key
+        attr_writer :primary_key
+
         # Sets the name of the primary key column to use to the given value,
         # or (if the value is nil or false) to the value returned by the given
         # block.
@@ -48,9 +53,11 @@ def get_primary_key(base_name) #:nodoc:
         #     set_primary_key "sysid"
         #   end
         def set_primary_key(value = nil, &block)
-          define_attr_method :primary_key, value, &block
+          @primary_key ||= ''
+          self.original_primary_key = @primary_key
+          value &&= value.to_s
+          self.primary_key = block_given? ? instance_eval(&block) : value
         end
-        alias :primary_key= :set_primary_key
       end
     end
   end

activerecord/test/cases/base_test.rb

@@ -1073,10 +1073,14 @@ def test_define_attr_method_with_value
   end
 
   def test_define_attr_method_with_block
-    k = Class.new( ActiveRecord::Base )
-    k.primary_key = "id"
-    k.send(:define_attr_method, :primary_key) { "sys_" + original_primary_key }
-    assert_equal "sys_id", k.primary_key
+    k = Class.new( ActiveRecord::Base ) do
+      class << self
+        attr_accessor :foo_key
+      end
+    end
+    k.foo_key = "id"
+    k.send(:define_attr_method, :foo_key) { "sys_" + original_foo_key }
+    assert_equal "sys_id", k.foo_key
   end
 
   def test_set_table_name_with_value

activerecord/test/cases/inheritance_test.rb

@@ -219,6 +219,10 @@ def test_alt_eager_loading
     switch_to_default_inheritance_column
   end
 
+  def test_inherits_custom_primary_key
+    assert_equal Subscriber.primary_key, SpecialSubscriber.primary_key
+  end
+
   def test_inheritance_without_mapping
     assert_kind_of SpecialSubscriber, SpecialSubscriber.find("webster132")
     assert_nothing_raised { s = SpecialSubscriber.new("name" => "And breaaaaathe!"); s.id = 'roger'; s.save }