random_page_cost not set from configfile

Question

if i set random_page_cost = 1.1 in my postgresql.conf, it is not beeing set, not after restart, not after select pg_reload_conf();.
It is however set, if i put it in the configfile bevor creating a new cluster.

If i update it via ALTER SYSTEM SET random_page_cost = 1.1; select pg_reload_conf();, it is set correctly.

Can someone please guide me to how to find out, WHY?

(I already started with -d 5, hoping i find something interesting in the startup-logs, why the value is beeing ignored, but i found nothing.

Thanks in advance.

Regards,
Stefan

Answer 1

Parameters can be set on many levels that override a setting in postgresql.conf:

• with ALTER SYSTEM
• during server start
• on the database
• on the user
• with SET or SET LOCAL

To determine what overrides the value from postgresql.conf, run

SELECT source, sourcefile, sourceline
FROM pg_settings
WHERE name = 'random_page_cost';

You can undo a setting from ALTER SYSTEM with

ALTER SYSTEM RESET random_page_cost;

Settings on the database or user can be undone with ALTER DATABASE/ROLE ... RESET ....

Once you have undone all overriding settings, the setting from postgresql.conf will prevail.