No need to set @arel_engine to nil twice. Committed by mistake in 3968825f

activerecord/lib/active_record/base.rb

@@ -1388,7 +1388,7 @@ def column_methods_hash #:nodoc:
       def reset_column_information
         undefine_attribute_methods
         @column_names = @columns = @columns_hash = @content_columns = @dynamic_methods_hash = @inheritance_column = nil
-        @arel_engine = @active_relation = @arel_engine = nil
+        @arel_engine = @active_relation = nil
       end
 
       def reset_column_information_and_inheritable_attributes_for_all_subclasses#:nodoc: