Re: GB18030-2022 Support in PostgreSQL

I have created a patch https://commitfest.postgresql.org/patch/5954/. CommitFests requested a rebase, so I rebased the code and created the v2 patch.

BTW, I have tested all 66 new characters, 9 not-required characters and 18 changed characters in a way as:

evantest=# SELECT encode(convert_from(decode('82359632', 'hex'), 'GB18030')::bytea, 'hex');
 encode
--------
 e9bfab
(1 row)

All encoded correctly.

Chao Li (Evan)

I did more researches about the changes in 2022 over 2000, here is a summary:

* 66 new characters have been added in 2022. All these are 4 bytes characters. As the map files store only 2 bytes GB code mappings, 4 bytes GB code mapping are calculated, thus these chars can be properly encoded/decoded without this patch, I tested that.

* 9 characters are no longer required by 2022, but application may decide to retain them or not. As the ucm file (https://github.com/unicode-org/icu/blob/main/icu4c/source/data/mappings/gb18030-2022.ucm) retains them, we also retain them.

* Unicode mappings for 18 characters have changed. Only these changes will cause backward compatibility issues. However, half of them are rarely used punctuation marks and rests are glyphs that I cannot recognize as a native Chinese speaker. So these changes should not significantly impact most existing databases.

I added a test case with a mapping changed char, and the test passes:

% make check

...

# All 229 tests passed.

For more details on the standard change, see https://ken-lunde.medium.com/the-gb-18030-2022-standard-3d0ebaeb4132

I am attaching the patch file.

Chao Li (Evan)

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