Re: BUG #18724: High data disk utilization during log writing

Thank you for your reply. I think I'm close to solving the mystery.
As a result of the research, I found that in addition to recording logs,
there is also a record in the pgss_query_texts.stat file, which is located
in the data directory.
And at the moment, this is what I consider to be the reason for the high
utilization of the data disk.
But this file is not used at all if I unload pg_stat_statements module
from shared_preload_libraries

пн, 25 нояб. 2024 г. в 19:47, Christophe Pettus <xof(at)thebuild(dot)com>:

>
>
> > On Nov 25, 2024, at 04:26, PG Bug reporting form <noreply(at)postgresql(dot)org>
> wrote:
> > The lsof utility did not help in investigating this problem, as did
> > restarting the server
> > Setting log_min_duration_statement = -1 shows a significant decrease in
> the
> > load on the data disk
> > So I can't assume why data disk (/dev/vdb1 /data) utilized up to 60-80%
> > while statements are logged to separate block device (/dev/vdc1
> > /var/log/postgresql) and need some help to get off the ground
>
> The question seems to answer itself here: You are logging every statement
> to the text logs, and it is very likely that the lines in the text log are
> larger than the actual data for that statement being written to the data
> disk. It can be very expensive to log every statement, especially when you
> have a significant query load (which you do here).