postgres 9.3. resets log_min_duration_statement after receiving SIGHUP
After reload you get have settings from config (default)
you must use false as 3 parameter - it is is_local - just for current 
transaction


sqldb=# select current_setting('log_min_duration_statement');
 current_setting 
-----------------
 -1
(1 row)

sqldb=# select set_config('log_min_duration_statement', '1000', false);
 set_config 
------------
 1s
(1 row)

sqldb=# select current_setting('log_min_duration_statement');
 current_setting 
-----------------
 1s
(1 row)