| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Andrei Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Teodor Sigaev <teodor(at)sigaev(dot)ru>, David Rowley <dgrowleyml(at)gmail(dot)com>, "a(dot)rybakina" <a(dot)rybakina(at)postgrespro(dot)ru>, Белялов Дамир Наилевич <d(dot)belyalov(at)postgrespro(dot)ru> |
| Subject: | Re: POC: GROUP BY optimization |
| Date: | 2024-01-26 15:41:05 |
| Message-ID: | CA+TgmoZHC=Lp83eucToAwNzoMeiaRMeTXqhPeGSquGLuGRgmTg@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Fri, Jan 26, 2024 at 10:38 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Sadly, that's not a small task:
>
> * We'd need to put effort into assigning more realistic procost
> values --- preferably across the board, not just comparison functions.
> As long as all the comparison functions have procost 1.0, you're
> just flying blind.
>
> * As you mentioned, there'd need to be some accounting for the
> likely size of varlena inputs, and especially whether they might
> be toasted.
>
> * cost_sort knows nothing of the low-level sort algorithm improvements
> we've made in recent years, such as abbreviated keys.
>
> That's a lot of work, and I think it has to be done before we try
> to build infrastructure on top, not afterwards.
OK, that makes sense to me. Thanks.
--
Robert Haas
EDB: http://www.enterprisedb.com
| From | Date | Subject | |
|---|---|---|---|
| Next Message | David G. Johnston | 2024-01-26 15:43:13 | Re: Add new error_action COPY ON_ERROR "log" |
| Previous Message | Tom Lane | 2024-01-26 15:38:23 | Re: POC: GROUP BY optimization |