3 files changed, 33 insertions, 11 deletions
diff --git a/activerecord/lib/active_record/attribute_set.rb b/activerecord/lib/active_record/attribute_set.rb
index 026b3cf014..be581ac2a9 100644
--- a/activerecord/lib/active_record/attribute_set.rb
+++ b/activerecord/lib/active_record/attribute_set.rb
@@ -91,6 +91,10 @@ module ActiveRecord
       AttributeSet.new(new_attributes)
     end
 
+    def ==(other)
+      attributes == other.attributes
+    end
+
     protected
 
     attr_reader :attributes
diff --git a/activerecord/lib/active_record/attribute_set/builder.rb b/activerecord/lib/active_record/attribute_set/builder.rb
index f974b7a876..3bd7c7997b 100644
--- a/activerecord/lib/active_record/attribute_set/builder.rb
+++ b/activerecord/lib/active_record/attribute_set/builder.rb
@@ -68,10 +68,29 @@ module ActiveRecord
       end
     end
 
+    def ==(other)
+      if other.is_a?(LazyAttributeHash)
+        materialize == other.materialize
+      else
+        materialize == other
+      end
+    end
+
     protected
 
     attr_reader :types, :values, :additional_types, :delegate_hash
 
+    def materialize
+      unless @materialized
+        values.each_key { |key| self[key] }
+        types.each_key { |key| self[key] }
+        unless frozen?
+          @materialized = true
+        end
+      end
+      delegate_hash
+    end
+
     private
 
     def assign_default_value(name)
@@ -85,16 +104,5 @@ module ActiveRecord
         delegate_hash[name] = Attribute.uninitialized(name, type)
       end
     end
-
-    def materialize
-      unless @materialized
-        values.each_key { |key| self[key] }
-        types.each_key { |key| self[key] }
-        unless frozen?
-          @materialized = true
-        end
-      end
-      delegate_hash
-    end
   end
 end
diff --git a/activerecord/test/cases/attribute_set_test.rb b/activerecord/test/cases/attribute_set_test.rb
index 5a0e463a48..7a24b85a36 100644
--- a/activerecord/test/cases/attribute_set_test.rb
+++ b/activerecord/test/cases/attribute_set_test.rb
@@ -239,5 +239,15 @@ module ActiveRecord
       assert_equal 2, new_attributes.fetch_value(:foo)
       assert_equal 3, new_attributes.fetch_value(:bar)
     end
+
+    test "comparison for equality is correctly implemented" do
+      builder = AttributeSet::Builder.new(foo: Type::Integer.new, bar: Type::Integer.new)
+      attributes = builder.build_from_database(foo: "1", bar: "2")
+      attributes2 = builder.build_from_database(foo: "1", bar: "2")
+      attributes3 = builder.build_from_database(foo: "2", bar: "2")
+
+      assert_equal attributes, attributes2
+      assert_not_equal attributes2, attributes3
+    end
   end
 end