Re: Get table total page quantity and cached page quantity

Answer is pretty clear, thank you David.

On Mon, Aug 16, 2021 at 12:31 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:

> On Sun, 15 Aug 2021 at 23:41, otar shavadze <oshavadze(at)gmail(dot)com> wrote:
> > SELECT
> > (SELECT relpages FROM pg_class where oid =
> 'public.my_table'::regclass::oid ) AS table_pages_quantity_total,
> > (SELECT COUNT(DISTINCT relblocknumber) FROM pg_buffercache WHERE
> relfilenode = (
> > SELECT relfilenode FROM pg_class WHERE oid =
> 'public.my_table'::regclass::oid -- (SELECT rel_oid FROM my_cte)
> > ) ) AS table_pages_quantity_in_cache;
> >
> > This shows that table have only one page, while second column shows 3
> unique pages in buffer cache. Seems I'm measuring those numbers
> incorrectly(?) can you please help, which column is incorrect (or may be
> both) ?
>
> This question likely is more suited to the pgsql-general mailing list.
> My answer in [1] likely will clear this up for you.
>
> If you need further information, please ask on that thread.
>
> David
>
> [1]
> https://www.postgresql.org/message-id/CAApHDvpHddfoZOviYXiz2dCr9emrrbnJ7n3HkS8KNsD9W1wscA@mail.gmail.com
>