To log all slow queries add to your config postgresql.conf:

log_min_duration_statement = 5s

Be careful with the option log_duration = on since it will log all request (disk can be come full very quickly)

You need to have logging_collector = on

Then reload postgres:

SELECT pg_reload_conf()

To very run:

postgres> SHOW log_min_duration_statement;
+----------------------------+
| log_min_duration_statement |
|----------------------------|
| 5s                         |
+----------------------------+

Test with:

postgres> select pg_sleep(5);

Logs will show something like:

time=2024-07-12 12:53:32 UTC, pid=2458932  db=postgres, usr=postgres, client=10.16.1.135 , app=pgcli, line=3 LOG:  duration: 5009.768 ms  statement: select pg_sleep(5)