* ddl: always try a better algorithm * ddl: adapt the test * ddl: fix TestAlterAlgorithm * ddl: better test fix * ddl: typo * ddl: update comment Co-authored-by: bb7133 <bb7133@gmail.com> * executor: typo Co-authored-by: djshow832 <zhangming@pingcap.com> Co-authored-by: bb7133 <bb7133@gmail.com> Co-authored-by: djshow832 <zhangming@pingcap.com> Co-authored-by: ti-srebot <66930949+ti-srebot@users.noreply.github.com>