On his blog today Brian Moon takes a look at the mysqlnd driver that comes with PHP 5.3 by default and some strangeness he found when trying to fetch results.

I have spoken in the past (see my slides and interview: MySQL Tips and Tricks) about using mysql_unbuffered_query or using mysqli_query with the MYSQLI_USE_RESULT flag [...] So, my natural thought was that using MYSQLI_USE_RESULT with fetch_all would yield the most awesome performance ever. The data would not be buffered and it would get put into a PHP array in C instead of native code.

He had hoped that the fetch_all would cooperate with the MYSQL_USE_RESULT setting, but it seemed to only work with the MYSQLI_STORE_RESULT default. He even filed a bug on the matter which was marked bogus and then reopened. He hopes to show, based on test results, that the result could be much faster.