fewer funcalls to the cached attributes variable

1 files changed, 1 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
index 506f6e878f..2001b6522d 100644
--- a/activerecord/lib/active_record/attribute_methods/read.rb
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -20,7 +20,7 @@ module ActiveRecord
         # be cached. Usually caching only pays off for attributes with expensive conversion
         # methods, like time related columns (e.g. +created_at+, +updated_at+).
         def cache_attributes(*attribute_names)
-          attribute_names.each {|attr| cached_attributes << attr.to_s}
+          cached_attributes.merge attribute_names.map { |attr| attr.to_s }
         end
 
         # Returns the attributes which are cached. By default time related columns