On Wed, Oct 14, 2020 at 3:57 PM Thomas Kellerer <shammat@gmx.net> wrote:
Thomas Kellerer schrieb am 14.10.2020 um 15:55: > Raul Kaubi schrieb am 14.10.2020 um 12:22: >> Is there a simple way to dynamically get for example parameter >> „shared buffers“ value (megabytes or gigabytes) to bytes, for >> monitoring perspective..?> >> >> >> At the moment, this gives me value in GB. >> >> # psql -U postgres -Atc "show shared_buffers;" >> 1GB >> >> This value may as well be in MB. So I am looking a way to dynamically get the value in bytes. > > Instead of using "show" you can use a SELECT with pg_size_bytes(): > > select pg_size_bytes(setting) > from pg_settings > where name = 'shared_buffers';
Ah, forgot that shared_buffers is in 8K pages.
So you actually need:
select pg_size_bytes(setting) * 8192 from pg_settings where name = 'shared_buffers';
Actually, it doesn't have to be in 8k pages, that depends on the build options. So if you want to be perfectly correct, you should probably multiply with current_setting('block_size') instead of a hardcoded 8192 :)
