has_many nullify associations keys using ARel.

activerecord/lib/active_record/associations/has_many_association.rb

@@ -40,11 +40,11 @@ def count_records
           # we are certain the current target is an empty array. This is a
           # documented side-effect of the method that may avoid an extra SELECT.
           @target ||= [] and loaded if count == 0
-          
+
           if @reflection.options[:limit]
             count = [ @reflection.options[:limit], count ].min
           end
-          
+
           return count
         end
 
@@ -69,11 +69,11 @@ def delete_records(records)
             when :delete_all
               @reflection.klass.delete(records.map { |record| record.id })
             else
-              ids = quoted_record_ids(records)
-              @reflection.klass.update_all(
-                "#{@reflection.primary_key_name} = NULL", 
-                "#{@reflection.primary_key_name} = #{owner_quoted_id} AND #{@reflection.klass.primary_key} IN (#{ids})"
-              )
+              relation = arel_table(@reflection.table_name)
+              relation.conditions(relation[@reflection.primary_key_name].eq(@owner.id).
+                  and(Arel::In.new(relation[@reflection.klass.primary_key], records.map(&:id)))
+              ).update(relation[@reflection.primary_key_name] => nil)
+
               @owner.class.update_counters(@owner.id, cached_counter_attribute_name => -records.size) if has_cached_counter?
           end
         end
@@ -88,11 +88,11 @@ def construct_sql
               @finder_sql = interpolate_sql(@reflection.options[:finder_sql])
 
             when @reflection.options[:as]
-              @finder_sql = 
+              @finder_sql =
                 "#{@reflection.quoted_table_name}.#{@reflection.options[:as]}_id = #{owner_quoted_id} AND " +
                 "#{@reflection.quoted_table_name}.#{@reflection.options[:as]}_type = #{@owner.class.quote_value(@owner.class.base_class.name.to_s)}"
               @finder_sql << " AND (#{conditions})" if conditions
-            
+
             else
               @finder_sql = "#{@reflection.quoted_table_name}.#{@reflection.primary_key_name} = #{owner_quoted_id}"
               @finder_sql << " AND (#{conditions})" if conditions