habtm delete method integrated with ARel.

activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb

@@ -34,7 +34,7 @@ def construct_find_options!(options)
           options[:readonly]   = finding_with_ambiguous_select?(options[:select] || @reflection.options[:select])
           options[:select]   ||= (@reflection.options[:select] || '*')
         end
-        
+
         def count_records
           load_target.size
         end
@@ -85,9 +85,10 @@ def delete_records(records)
           if sql = @reflection.options[:delete_sql]
             records.each { |record| @owner.connection.delete(interpolate_sql(sql, record)) }
           else
-            ids = quoted_record_ids(records)
-            sql = "DELETE FROM #{@owner.connection.quote_table_name @reflection.options[:join_table]} WHERE #{@reflection.primary_key_name} = #{owner_quoted_id} AND #{@reflection.association_foreign_key} IN (#{ids})"
-            @owner.connection.delete(sql)
+            relation = arel_table(@reflection.options[:join_table])
+            relation.conditions(relation[@reflection.primary_key_name].eq(@owner.id).
+              and(Arel::In.new(relation[@reflection.association_foreign_key], records.map(&:id)))
+            ).delete
           end
         end