SET @mroonga_log_file_backup = @@mroonga_log_file;
SET GLOBAL mroonga_log_file = "new-mroonga.log";
SHOW GLOBAL VARIABLES LIKE 'mroonga_log_file';
Variable_name	Value
mroonga_log_file	new-mroonga.log
SET GLOBAL mroonga_log_file = @mroonga_log_file_backup;
