Postgres 14 WAL FILE cannot change min wal size(in WAL DIRECTORY) after changing propperties min_wal_size max_wal_size

Question

I'm completely new in Postgres optimization. I was reading a lot about checkpoint and WAL files. I found a query to examine the ratio of checkpoints time to requested (exceeded WAL max size)

SELECT checkpoints_timed, checkpoints_req
FROM pg_stat_bgwriter;

checkpoints_timed	checkpoints_req
20496	53

In order to minimalize requested checkpoint I changed postgres configuration to:

checkpoint_timeout = 15min  
max_wal_size = 2GB  
min_wal_size = 200MB  

But when I check WAL dir space is still 83MB (as the default value from configuration).

select sum(size)
from pg_ls_waldir(); 

Can anyone explain why WAL directory size is still ~83MB and not increasing to 200MB?

I noted that changing parameters has triggered 2 checkpoints_req so I guess that max_wal_size is still 1GB?

Answer 1

The poorly-named checkpoints_req includes checkpoints requested due to WAL usage, as well as ones requested by things like shutdowns, backups, or manual CHECKPOINT commands. If your checkpoints were performed due to any of those latter causes, there is no reason to think it would imply anything at all about WAL size.

Also, since the vast majority of checkpoints were timed, why are you mucking about with the size parameters anyway? There doesn't seem to be a problem here that needs to be solved. That isn't optimization, just heckling.