postgresql configuration / slow log

[vladimir.d]

We need to enable postgresql slow query logging and we have done the following:

$ docker exec -ti postgresql bash
$ psql -d MY_DATABASE_NAME

psql (12.10 (Ubuntu 12.10-1.pgdg20.04+1+b1))
Type "help" for help.

MY_DATABASE_NAME =# ALTER DATABASE MY_DATABASE_NAME SET log_min_duration_statement = 5000;

MY_DATABASE_NAME =# SELECT pg_sleep(15);

But the slow log file didn't appear anywhere (/run/postgresql, /var/log/postgresql, /var/lib/postgresql/12/main/).

We need to set logging_collector to on in the postgresql config /etc/postgresql/12/main/postgresql.conf which is read-only.

Also please advise how to amend postgresql configuration in reboot/upgrade safe way.