sqlite3_create_collation andsqlite3_create_collation_v2 are described here:https://sqlite.org/c3ref/create_collation.html

FYI, the test suite already exercise clearing a collation callback and re-registering a collation callback.

BTW, I'd like to change thefinally label at the end ofpysqlite_connection_init_impl toerror, for consistency with the rest of the code base.

I see that the beginning of the function does some busywork convertingname to uppercase and checking for allowed characters. Is that limitation there only to make that sure comparison of keys in thecollations dict matchsqlite3_strnicmp? If so,PyUnicode_AsUTF8(name) could be used instead.

Yes, I noticed that part as well. I haven't investigated why this was added in the first place. I'll try withPyUnicode_AsUTF8(). Thanks!

As for thefinally→error rename, I'd sayfinally is a better name when it's also executed in the non-error case...

True.

FYI, the collation code (including the uppercase conversion / check), was added topysqlite in 2006, when it still was an external project. The code seems to have been borrowed directly fromapsw.

UPDATE:
SQLite accepts UTF8 collation names; there should be no reason to limit collation names to ASCII. Maybe there was a bug or a limitation in earlier SQLite versions. Theapsw code has removed this limitation and now accepts UTF8 names. We can do that as well. I'll open up an issue for that.

UPDATE AGAIN:
I've createdissue 44688.I'll open a PR once this is merged. PR#27395 opened.

Thank you!