clearTable is mainly used for clearing data between tests. In this case,
there are very few or zero records, and DELETE FROM is quicker than
TRUNCATE, which works by deleting and recreating the table.
This materially speeds up test execution, at least on MySQL.
Implemented in SS3 at 815da76b056a716c8831d22bbf93528912cbcb28
This variant of showqueries will include a backtrace after each query.
This is extremely verbose but can be helpful when diagnosing where
queries have come from.
This is something that I have frequently added as a local hack on my
environment, I figured that exposing it as a formal feature would be
useful.