[patches] [PATCH 3/4] tuple: check key for sequential parts on compile time

[Vladimir Davydov]

On Tue, Feb 13, 2018 at 06:28:37PM +0300, Vladislav Shpilevoy wrote:
> --- a/src/box/tuple_extract_key.cc
> +++ b/src/box/tuple_extract_key.cc
> @@ -57,6 +57,7 @@ tuple_extract_key_sequential(const struct tuple *tuple,
>   * General-purpose implementation of tuple_extract_key()
>   * @copydoc tuple_extract_key()
>   */
> +template <bool contains_sequential_parts>
>  static char *
>  tuple_extract_key_slowpath(const struct tuple *tuple,
>  			   const struct key_def *key_def, uint32_t *key_size)
> @@ -73,17 +74,21 @@ tuple_extract_key_slowpath(const struct tuple *tuple,
>  			tuple_field_raw(format, data, field_map,
>  					key_def->parts[i].fieldno);
>  		const char *end = field;
> -		/*
> -		 * Skip sequential part in order to minimize
> -		 * tuple_field_raw() calls.
> -		 */
> -		for (; i < key_def->part_count - 1; i++) {
> -			if (key_def->parts[i].fieldno + 1 !=
> -				key_def->parts[i + 1].fieldno) {
> -				/* End of sequential part */
> -				break;
> +		if (contains_sequential_parts) {
> +			/*
> +			 * Skip sequential part in order to
> +			 * minimize tuple_field_raw() calls.
> +			 */
> +			for (; i < key_def->part_count - 1; i++) {
> +				if (key_def->parts[i].fieldno + 1 !=
> +					key_def->parts[i + 1].fieldno) {
> +					/*
> +					 * End of sequential part.
> +					 */
> +					break;
> +				}
> +				mp_next(&end);

In comparison to tuple_field_raw(), which is called on each iteration,
the cost of the loop you're optimizing out should be negligible. Is it
really worth it? Did you run any tests that showed a performance gain?