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

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tomas Vondra <tomas(at)vondra(dot)me>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: should we have a fast-path planning for OLTP starjoins?
Date: 2025-11-24 20:55:25
Message-ID: CA+TgmoYq+e3kiSpTD5cZS6Lz6PAiPzWjROsZus0PVQXa8VCMsw@mail.gmail.com
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On Sun, Nov 23, 2025 at 9:39 AM Tomas Vondra <tomas(at)vondra(dot)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

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