On Wed, Oct 14, 2020 at 3:57 PM Thomas Kellerer <shammat@xxxxxxx> 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 :)
