A similar problem also exists in "mariadb|5.5.44-7.2|x86_64". Since the update to the above version of MariaDB, group_concat_max_len has the default value of 4 instead of 1024 as specified in the Mysql documentation. However, after adding group_concat_max_len=32768 to my.cnf and restarting mysql the value from my.cnf is used.