3 files changed, 5 insertions, 10 deletions
diff --git a/activerecord/lib/active_record/associations/association_collection.rb b/activerecord/lib/active_record/associations/association_collection.rb
index f346a19a3a..4ce3b34819 100644
--- a/activerecord/lib/active_record/associations/association_collection.rb
+++ b/activerecord/lib/active_record/associations/association_collection.rb
@@ -478,13 +478,10 @@ module ActiveRecord
           callback(:before_add, record)
           yield(record) if block_given?
           @target ||= [] unless loaded?
-          index = @target.index(record)
-          unless @reflection.options[:uniq] && index
-            if index
-              @target[index] = record
-            else
+          if index = @target.index(record)
+            @target[index] = record
+          else
              @target << record
-            end
           end
           callback(:after_add, record)
           set_inverse_instance(record, @owner)
diff --git a/activerecord/lib/active_record/autosave_association.rb b/activerecord/lib/active_record/autosave_association.rb
index 7517896235..062b010436 100644
--- a/activerecord/lib/active_record/autosave_association.rb
+++ b/activerecord/lib/active_record/autosave_association.rb
@@ -377,10 +377,6 @@ module ActiveRecord
           if association.updated?
             association_id = association.send(reflection.options[:primary_key] || :id)
             self[reflection.primary_key_name] = association_id
-            # TODO: Removing this code doesn't seem to matter...
-            if reflection.options[:polymorphic]
-              self[reflection.options[:foreign_type]] = association.class.base_class.name.to_s
-            end
           end
 
           saved if autosave
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index c589b32dd8..5898ec3732 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -1255,6 +1255,8 @@ MSG
             replace_named_bind_variables(statement, values.first)
           elsif statement.include?('?')
             replace_bind_variables(statement, values)
+          elsif statement.blank?
+            statement
           else
             statement % values.collect { |value| connection.quote_string(value.to_s) }
           end