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

Hi

Thanks for all the replies.

So at first, I did this:
select (pg_size_bytes(setting) * (select setting from pg_settings where
name = 'block_size')::int) as shared_buffers from pg_settings where name =
'shared_buffers';

But as I understood, that the preferred way would be this, correct..? (at
least, it seems a lot simpler, I agree)
SELECT pg_size_bytes(current_setting('shared_buffers'))

Regards
Raul

Kontakt Tom Lane (<tgl(at)sss(dot)pgh(dot)pa(dot)us>) kirjutas kuupäeval K, 14. oktoober
2020 kell 18:23:

> Magnus Hagander <magnus(at)hagander(dot)net> writes:
> > On Wed, Oct 14, 2020 at 5:10 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> It's fairly annoying that this doesn't work:
> >> regression=# select pg_size_bytes(setting||' '||unit) from pg_settings
> >> where name = 'shared_buffers';
>
> > Actually thinking though, surely *this* particular case can be spelled
> as:
> > SELECT pg_size_bytes(current_setting('shared_buffers'))
>
> Yeah, that might be the most recommendable way.
>
> > Or if doing it off pg_settings:
> > SELECT setting::bigint * pg_size_bytes(unit) from pg_settings where
> > name='shared_buffers'
>
> No, because that will fail for any unit other than '8kB', eg
>
> regression=# select pg_size_bytes('MB');
> ERROR: invalid size: "MB"
>
> > I'm not sure having pg_size_bytes() parse "16384 8kB" is reasonable, I
> have
> > a feeling that could lead to a lot of accidental entries giving the wrong
> > results.
>
> Yeah, that's definitely a risk. Given that current_setting() already does
> what's needed, that's probably a better answer.
>
> regards, tom lane
>
>
>