The tests jobs should fail under MariaDB/MySQL strict mode on CI db hosts. We need to populate the configuration bit under /etc/mysql/conf.d/ and announce it. Some extensions tests will most probably start falling magically.
There are 2 options to add:
sql_mode = 'TRADITIONAL'
which is really an alias to:
sql_mode = 'STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION'
Ideally, we would set too:
sql_mode = 'TRADITIONAL, ONLY_FULL_GROUP_BY';
However, this last one only works properly on MySQL >= 5.7, and on lower versions of MySQL and MariaDB it doesn't detect functional dependencies properly (https://stackoverflow.com/questions/40084093/does-mariadb-not-support-functional-dependencies-in-select-statements-when-group ) , so it could create false positives (it would be nice to try it however, as it will likely detect true issues, but I agree it shouldn't be pussed hard, unlike the previous one, until all supported versions do the right thing.