This is a continuation of
If one takes a basic testcase with a merged derived table (or a view):
they can see that the code calls create_tmp_table(... do_not_open=true. ...) for the derived table (or the merged view). This may add extra overhead (although we are not sure how much ATM).
This effect was introduced in MariaDB 5.3, in this commit:
MySQL 5.6 doesn't have this optimization, so they dont have this problem.