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

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