Re: should we have a fast-path planning for OLTP starjoins?

Robert Haas <robertmhaas@gmail.com>

From: Robert Haas <robertmhaas@gmail.com>
To: Tomas Vondra <tomas@vondra.me>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2025-11-24T20:55:25Z
Lists: pgsql-hackers
On Sun, Nov 23, 2025 at 9:39 AM Tomas Vondra <tomas@vondra.me> wrote:
> > 1. I do not think I believe the premise that the dimension tables
> > typically won't have restriction clauses.  ISTM that a typical
> > query might be like
> >
> >       select sum(o.total_price) from
> >       orders o
> >       join customers c on c.id = o.c_id
> >       join products p on p.id = o.p_id
> >       where c.customer_name = 'Wile E Coyote'
> >       and p.product_name = 'Rocket Skates';
> >
>
> Good question. I don't have a great evidence such joins to dimensions
> (without additional restrictions) are a common case. It's partially a
> guess and partially based on my past experience.

In my experience, restriction clauses on dimension tables are very common.

-- 
Robert Haas
EDB: http://www.enterprisedb.com