I tested this patch locally and it works for me. However I doubt if it really improve performance. The original code "contain_volatile_functions((Node *) rte->values_lists)" recursively work through rte-values_list, and this patch move contain_volatile_functions() into the for loop, and checks against every item of rte->values_list. As entries of values_list could just be Const, contain_volatile_functions() will then return immediately, so that this changes reduces total calls to contain_volatile_functions(). From this perspective, this patch may improve the performance.
On the other side, let's say a case where a values_list contains 10 items, and the last item is volatile. With the original code, it won't enter the for loop, nothing will be built; with this patch, operations have been performed on the first 9 items, but eventually it returns NULL when hit the last item. So in this case, performance could be worse. Overall, I am afraid the burden could beat the gain. The new status of this patch is: Waiting on Author
