Hi Elena and all,
The bug behind isn't after all behind my query not running. It runs perfectly until 10.1.9 and after it, it throws an error.
MariaDB 10.1.9: OK
MariaDB >= 10.1.10: SQL Error (1062): Duplicate entry '191' for key 'group_key'
10.1.9 EXPLAIN FORMAT=JSON
10.1.10 and 10.1.11 EXPLAIN FORMAT=JSON
Any idea what might be?