Cache unserialized attributes

3 files changed, 26 insertions, 20 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
index 3da3d9d8cc..083c8f88b1 100644
--- a/activerecord/lib/active_record/attribute_methods/read.rb
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -26,8 +26,7 @@ module ActiveRecord
         # Returns the attributes which are cached. By default time related columns
         # with datatype <tt>:datetime, :timestamp, :time, :date</tt> are cached.
         def cached_attributes
-          @cached_attributes ||=
-            columns.select{|c| attribute_types_cached_by_default.include?(c.type)}.map{|col| col.name}.to_set
+          @cached_attributes ||= columns.select { |c| cacheable_column?(c) }.map { |col| col.name }.to_set
         end
 
         # Returns +true+ if the provided attribute is being cached.
@@ -37,7 +36,7 @@ module ActiveRecord
 
         protected
           def define_method_attribute(attr_name)
-            if self.serialized_attributes[attr_name]
+            if serialized_attributes.include?(attr_name)
               define_read_method_for_serialized_attribute(attr_name)
             else
               define_read_method(attr_name.to_sym, attr_name, columns_hash[attr_name])
@@ -49,9 +48,14 @@ module ActiveRecord
           end
 
         private
+          def cacheable_column?(column)
+            serialized_attributes.include?(column.name) || attribute_types_cached_by_default.include?(column.type)
+          end
+
           # Define read method for serialized attribute.
           def define_read_method_for_serialized_attribute(attr_name)
-            generated_attribute_methods.module_eval("def #{attr_name}; unserialize_attribute('#{attr_name}'); end", __FILE__, __LINE__)
+            access_code = "@attributes_cache['#{attr_name}'] ||= unserialize_attribute('#{attr_name}')"
+            generated_attribute_methods.module_eval("def #{attr_name}; #{access_code}; end", __FILE__, __LINE__)
           end
 
           # Define an attribute reader method.  Cope with nil column.
@@ -92,7 +96,7 @@ module ActiveRecord
 
       # Returns true if the attribute is of a text column and marked for serialization.
       def unserializable_attribute?(attr_name, column)
-        column.text? && self.class.serialized_attributes[attr_name]
+        column.text? && self.class.serialized_attributes.include?(attr_name)
       end
 
       # Returns the unserialized object of the attribute.
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index fe888ca369..5da4eb169b 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -415,6 +415,11 @@ module ActiveRecord #:nodoc:
     class_inheritable_accessor :default_scoping, :instance_writer => false
     self.default_scoping = []
 
+    # Returns a hash of all the attributes that have been specified for serialization as
+    # keys and their class restriction as values.
+    class_attribute :serialized_attributes
+    self.serialized_attributes = {}
+
     class << self # Class methods
       delegate :find, :first, :last, :all, :destroy, :destroy_all, :exists?, :delete, :delete_all, :update, :update_all, :to => :scoped
       delegate :find_each, :find_in_batches, :to => :scoped
@@ -526,12 +531,6 @@ module ActiveRecord #:nodoc:
         serialized_attributes[attr_name.to_s] = class_name
       end
 
-      # Returns a hash of all the attributes that have been specified for serialization as
-      # keys and their class restriction as values.
-      def serialized_attributes
-        read_inheritable_attribute(:attr_serialized) or write_inheritable_attribute(:attr_serialized, {})
-      end
-
       # Guesses the table name (in forced lower-case) based on the name of the class in the
       # inheritance hierarchy descending directly from ActiveRecord::Base. So if the hierarchy
       # looks like: Reply < Message < ActiveRecord::Base, then Message is used
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 9b3cc47c79..3c4fa4fd3f 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -419,12 +419,8 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     Topic.instance_variable_set "@cached_attributes", nil
   end
 
-  def test_time_related_columns_are_actually_cached
-    column_types = %w(datetime timestamp time date).map(&:to_sym)
-    column_names = Topic.columns.select{|c| column_types.include?(c.type) }.map(&:name)
-
-    assert_equal column_names.sort, Topic.cached_attributes.sort
-    assert_equal time_related_columns_on_topic.sort, Topic.cached_attributes.sort
+  def test_cacheable_columns_are_actually_cached
+    assert_equal cached_columns.sort, Topic.cached_attributes.sort
   end
 
   def test_accessing_cached_attributes_caches_the_converted_values_and_nothing_else
@@ -435,8 +431,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     assert cache.empty?
 
     all_columns = Topic.columns.map(&:name)
-    cached_columns = time_related_columns_on_topic
-    uncached_columns =  all_columns - cached_columns
+    uncached_columns = all_columns - cached_columns
 
     all_columns.each do |attr_name|
       attribute_gets_cached = Topic.cache_attribute?(attr_name)
@@ -594,8 +589,16 @@ class AttributeMethodsTest < ActiveRecord::TestCase
 
 
   private
+  def cached_columns
+    @cached_columns ||= (time_related_columns_on_topic + serialized_columns_on_topic).map(&:name)
+  end
+
   def time_related_columns_on_topic
-    Topic.columns.select{|c| [:time, :date, :datetime, :timestamp].include?(c.type)}.map(&:name)
+    Topic.columns.select { |c| [:time, :date, :datetime, :timestamp].include?(c.type) }
+  end
+
+  def serialized_columns_on_topic
+    Topic.columns.select { |c| Topic.serialized_attributes.include?(c.name) }
   end
 
   def in_time_zone(zone)