Re: [RFC] speed up count(*)

On Wed, Oct 20, 2021 at 2:23 PM Tomas Vondra <tomas.vondra@enterprisedb.com> wrote:
>
> Couldn't we simply inspect the visibility map, use the index data only
> for fully visible/summarized ranges, and inspect the heap for the
> remaining pages? That'd still be a huge improvement for tables with most
> only a few pages modified recently, which is a pretty common case.
>
> I think the bigger issue is that people rarely do COUNT(*) on the whole
> table. There are usually other conditions and/or GROUP BY, and I'm not
> sure how would that work.

Right. My (possibly hazy) recollection is that people don't have quite as high an expectation for queries with more complex predicates and/or grouping. It would be interesting to see what the balance is.

--
John Naylor
EDB: http://www.enterprisedb.com