Re: Parameter value from (mb/gb) to bytes

On Wed, Oct 14, 2020 at 3:57 PM Thomas Kellerer <shammat(at)gmx(dot)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 :)

--
Magnus Hagander
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