Hi, I'm reviewing "Multibyte charater set in levenshtein function" patch.
https://commitfest.postgresql.org/action/patch_view?id=304
The main logic seems to be good, but I have some comments about
the coding style and refactoring.
* levenshtein_internal() and levenshtein_less_equal_internal() are very similar. Can you merge the code? We can always
useless_equal_internal() if the overhead is ignorable. Did you compare them?
* There are many "if (!multibyte_encoding)" in levenshtein_internal(). How about split the function into two funcs for
single-bytechars and multi-byte chars? (ex. levenshtein_internal_mb() ) Or, we can always use multi-byte version if the
overheadis small.
* I prefer a struct rather than an array. "4 * m" and "3 * m" look like magic numbers for me. Could you name the
entrieswith definition of a struct? /* * For multibyte encoding we'll also store array of lengths of *
charactersand array with character offsets in first string * in order to avoid great number of pg_mblen calls. */
prev = (int *) palloc(4 * m * sizeof(int));
* There are some compiler warnings. Avoid them if possible.
fuzzystrmatch.c: In function ‘levenshtein_less_equal_internal’:
fuzzystrmatch.c:428: warning: ‘char_lens’ may be used uninitialized in
this function
fuzzystrmatch.c:428: warning: ‘offsets’ may be used uninitialized in
this function
fuzzystrmatch.c:430: warning: ‘curr_right’ may be used uninitialized
in this function
fuzzystrmatch.c: In function ‘levenshtein_internal’:
fuzzystrmatch.c:222: warning: ‘char_lens’ may be used uninitialized in
this function
* Coding style: Use "if (m == 0)" instead of "if (!m)" when the type
of 'm' is an integer.
* Need to fix the caution in docs.
http://developer.postgresql.org/pgdocs/postgres/fuzzystrmatch.html
| Caution: At present, fuzzystrmatch does not work well with
| multi-byte encodings (such as UTF-8).
but now levenshtein supports multi-byte encoding! We should
mention which function supports mbchars not to confuse users.
* (Not an issue for the patch, but...) Could you rewrite PG_GETARG_TEXT_P, VARDATA, and VARSIZE to PG_GETARG_TEXT_PP,
VARDATA_ANY,and VARSIZE_ANY_EXHDR? Unpacking versions make the core a bit faster.
--
Itagaki Takahiro