Ensure not to load the entire association when bulk updating existing records using nested attributes

1 files changed, 12 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index ee2d420194..70a460d41d 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -348,14 +348,24 @@ module ActiveRecord
         attributes_collection = attributes_collection.sort_by { |index, _| index.to_i }.map { |_, attributes| attributes }
       end
 
+      association = send(association_name)
+
+      existing_records = if association.loaded?
+        association.to_a
+      else
+        attribute_ids = attributes_collection.map {|a| a['id'] || a[:id] }.compact
+        attribute_ids.present? ? association.all(:conditions => {:id => attribute_ids}) : []
+      end
+
       attributes_collection.each do |attributes|
         attributes = attributes.with_indifferent_access
 
         if attributes['id'].blank?
           unless reject_new_record?(association_name, attributes)
-            send(association_name).build(attributes.except(*UNASSIGNABLE_KEYS))
+            association.build(attributes.except(*UNASSIGNABLE_KEYS))
           end
-        elsif existing_record = send(association_name).detect { |record| record.id.to_s == attributes['id'].to_s }
+        elsif existing_record = existing_records.detect { |record| record.id.to_s == attributes['id'].to_s }
+          association.send(:add_record_to_target_with_callbacks, existing_record) unless association.loaded?
           assign_to_or_mark_for_destruction(existing_record, attributes, options[:allow_destroy])
         else
           raise_nested_attributes_record_not_found(association_name, attributes['id'])