On Wed, Oct 14, 2020 at 5:10 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Magnus Hagander <mag...@hagander.net> writes: > > On Wed, Oct 14, 2020 at 3:57 PM Thomas Kellerer <sham...@gmx.net> wrote: > >> 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 > :) > > It's fairly annoying that this doesn't work: > > regression=# select pg_size_bytes(setting||' '||unit) from pg_settings > where name = 'shared_buffers'; > ERROR: invalid size: "16384 8kB" > DETAIL: Invalid size unit: "8kB". > HINT: Valid units are "bytes", "kB", "MB", "GB", and "TB". > > Maybe we should teach pg_size_bytes to cope with that. >
Actually thinking though, surely *this* particular case can be spelled as: SELECT pg_size_bytes(current_setting('shared_buffers')) Or if doing it off pg_settings: SELECT setting::bigint * pg_size_bytes(unit) from pg_settings where name='shared_buffers' 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. -- Magnus Hagander Me: https://www.hagander.net/ <http://www.hagander.net/> Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>