The third argument to sqlite3_result_text() is the length of the string passed as the second argument. Currently, we pass -1, so SQLite has to invoke strlen() to compute the length of the passed string. Suggesting to use PyUnicode_AsUTF8AndSize() iso. PyUnicode_AsUTF8() and pass the string size to avoid the superfluous strlen().

See also:
- https://sqlite.org/c3ref/result_blob.html

The difference between specifying negative and non-negative third argument of sqlite3_result_text() is that in the latter case the result can contain embedded NUL characters.

Could you please add a test for string containing embedded NUL?

Letting SQLite compute string length would work incorrect in case of embedded NULs, so I think that we should raise explicit error if sz > INT_MAX.

> Could you please add a test for string containing embedded NUL?

Of course, thanks for the heads up.

> I think that we should raise explicit error if sz > INT_MAX.

Yes, I thought about this. I do agree that raising OverflowError would be better. Thanks.

Serhiy, I've updated the PR, if you want to take a look. Thanks for your feedback.

New changeset 8f010dc920e1f6dc6a357e7cc1460a7a567c05c6 by Erlend Egeberg Aasland in branch 'main':
bpo-44822: Don't truncate `str`s with embedded NULL chars returned by `sqlite3` UDF callbacks (GH-27588)
https://github.com/python/cpython/commit/8f010dc920e1f6dc6a357e7cc1460a7a567c05c6

New changeset 2b1e713f877102bbca299f0f5d7db969d78db49f by Miss Islington (bot) in branch '3.10':
bpo-44822: Don't truncate `str`s with embedded NULL chars returned by `sqlite3` UDF callbacks (GH-27588)
https://github.com/python/cpython/commit/2b1e713f877102bbca299f0f5d7db969d78db49f

New changeset c352412123140e79dcce6188d17e3e6dbc3f4144 by Erlend Egeberg Aasland in branch '3.9':
[3.9] bpo-44822: Don't truncate `str`s with embedded NULL chars returned by `sqlite3` UDF callbacks (GH-27588). (GH-27639)
https://github.com/python/cpython/commit/c352412123140e79dcce6188d17e3e6dbc3f4144

Thanks, Serhiy!