Re: [PATCH v3 1/7] box: cleanup key_def virtual extract_key setter

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Tue, Apr 02, 2019 at 06:49:32PM +0300, Kirill Shcherbatov wrote:
> This patch inspired by 082cffca4dba attempts to simplify setting
> appropriate tuple_extract_key pointer for plain and json indexes
> in key_def_set_extract_func routine.
> Being split to plain and json blocks this code becomes easier
> to understand and extend.
> 
> In further patches we need to introduce is_multikey branch and
> without this refactoring required amendments turn the
> key_def_set_extract_func code into a mess.
> 
> Needed for #1257
> ---
>  src/box/tuple_extract_key.cc | 98 ++++++++++++++++++------------------
>  1 file changed, 49 insertions(+), 49 deletions(-)
> 
> diff --git a/src/box/tuple_extract_key.cc b/src/box/tuple_extract_key.cc
> index 0a8337102..836d4e565 100644
> --- a/src/box/tuple_extract_key.cc
> +++ b/src/box/tuple_extract_key.cc
> @@ -341,62 +341,62 @@ tuple_extract_key_slowpath_raw(const char *data, const char *data_end,
>  	return key;
>  }
>  
> -static const tuple_extract_key_t extract_key_slowpath_funcs[] = {
> -	tuple_extract_key_slowpath<false, false, false>,
> -	tuple_extract_key_slowpath<true, false, false>,
> -	tuple_extract_key_slowpath<false, true, false>,
> -	tuple_extract_key_slowpath<true, true, false>,
> -	tuple_extract_key_slowpath<false, false, true>,
> -	tuple_extract_key_slowpath<true, false, true>,
> -	tuple_extract_key_slowpath<false, true, true>,
> -	tuple_extract_key_slowpath<true, true, true>
> -};
> -
>  /**
>   * Initialize tuple_extract_key() and tuple_extract_key_raw()
>   */
> -void
> -key_def_set_extract_func(struct key_def *key_def)
> +template<bool contains_sequential_parts, bool has_optional_parts>
> +static void
> +key_def_set_extract_func_plain(struct key_def *def)
>  {
> -	if (key_def_is_sequential(key_def)) {
> -		if (key_def->has_optional_parts) {
> -			assert(key_def->is_nullable);
> -			key_def->tuple_extract_key =
> -				tuple_extract_key_sequential<true>;
> -			key_def->tuple_extract_key_raw =
> -				tuple_extract_key_sequential_raw<true>;
> -		} else {
> -			key_def->tuple_extract_key =
> -				tuple_extract_key_sequential<false>;
> -			key_def->tuple_extract_key_raw =
> -				tuple_extract_key_sequential_raw<false>;
> -		}
> +	assert(!def->has_json_paths);
> +	if (key_def_is_sequential(def)) {
> +		assert(contains_sequential_parts || def->part_count == 1);
> +		def->tuple_extract_key = tuple_extract_key_sequential
> +					<has_optional_parts>;
> +		def->tuple_extract_key_raw = tuple_extract_key_sequential_raw
> +					<has_optional_parts>;
>  	} else {
> -		int func_idx =
> -			(key_def_contains_sequential_parts(key_def) ? 1 : 0) +
> -			2 * (key_def->has_optional_parts ? 1 : 0) +
> -			4 * (key_def->has_json_paths ? 1 : 0);
> -		key_def->tuple_extract_key =
> -			extract_key_slowpath_funcs[func_idx];
> -		assert(!key_def->has_optional_parts || key_def->is_nullable);
> +		def->tuple_extract_key = tuple_extract_key_slowpath
> +					<contains_sequential_parts,
> +					 has_optional_parts, false>;
> +		def->tuple_extract_key_raw = tuple_extract_key_slowpath_raw
> +					<has_optional_parts, false>;
>  	}
> -	if (key_def->has_optional_parts) {
> -		assert(key_def->is_nullable);
> -		if (key_def->has_json_paths) {
> -			key_def->tuple_extract_key_raw =
> -				tuple_extract_key_slowpath_raw<true, true>;
> -		} else {
> -			key_def->tuple_extract_key_raw =
> -				tuple_extract_key_slowpath_raw<true, false>;
> -		}
> +}
> +
> +template<bool contains_sequential_parts, bool has_optional_parts>
> +static void
> +key_def_set_extract_func_json(struct key_def *def)
> +{
> +	assert(def->has_json_paths);
> +	def->tuple_extract_key = tuple_extract_key_slowpath
> +					<contains_sequential_parts,
> +					 has_optional_parts, true>;
> +	def->tuple_extract_key_raw = tuple_extract_key_slowpath_raw
> +					<has_optional_parts, true>;
> +}
> +
> +void
> +key_def_set_extract_func(struct key_def *key_def)
> +{
> +	int func_idx = (key_def_contains_sequential_parts(key_def) ? 1 : 0) +
> +			2 * (key_def->has_optional_parts ? 1 : 0);
> +	if (!key_def->has_json_paths) {
> +		void (*set_extract_func[])(struct key_def *) = {
> +			key_def_set_extract_func_plain<false, false>,
> +			key_def_set_extract_func_plain<true, false>,
> +			key_def_set_extract_func_plain<false, true>,
> +			key_def_set_extract_func_plain<true, true>,
> +		};
> +		set_extract_func[func_idx](key_def);
>  	} else {
> -		if (key_def->has_json_paths) {
> -			key_def->tuple_extract_key_raw =
> -				tuple_extract_key_slowpath_raw<false, true>;
> -		} else {
> -			key_def->tuple_extract_key_raw =
> -				tuple_extract_key_slowpath_raw<false, false>;
> -		}
> +		void (*set_extract_func[])(struct key_def *) = {
> +			key_def_set_extract_func_json<false, false>,
> +			key_def_set_extract_func_json<true, false>,
> +			key_def_set_extract_func_json<false, true>,
> +			key_def_set_extract_func_json<true, true>,
> +		};
> +		set_extract_func[func_idx](key_def);
>  	}
>  }

Yeah, this looks better. However, I'd also replace set_extract_func with
plain if-else-if - it would take only a couple lines longer, but look
more straightforward IMO.