The change in readwritesplit routing priorities, where hints have the
highest priority, gives users more options to control how readwritesplit
acts.
For example, this allows read-only stored procedures to be routed to
slaves by adding a hint to the query:
CALL myproc(); -- maxscale route to slave
The readwritesplit documentation also warns the user not to use routing
hints unless they can be absolutely sure that no damage will be done.