Enable slow_query_log tries to write to slow_log.CSV
I did these steps :


set global slow_query_log=0;
remove the slow log file in system
set global slow_query_log=1;


it works fine, so I tried these steps:

mysql&gt; set global slow_query_log=0;
Query OK, 0 rows affected (0.12 sec)

mysql&gt; set global slow_query_log_file='/tmp/slow.log';
Query OK, 0 rows affected (0.10 sec)

mysql&gt; set global slow_query_log=1;
Query OK, 0 rows affected (0.00 sec)


still works, and new slow log file is generated as /tmp/slow.log.

At last, the value of global variable log_output decides where to generate the general log and slow log's output, not the file format.