Re: Key joins

From: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
To: Joel Jacobson <joel(at)compiler(dot)org>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Cc: Arne Roland <arne(dot)roland(at)malkut(dot)net>, Anders Granlund <anders(dot)granlund(dot)0(at)gmail(dot)com>, Andreas Karlsson <andreas(at)proxel(dot)se>, Vik Fearing <vik(at)chouppes(dot)com>
Subject: Re: Key joins
Date: 2026-05-29 12:51:23
Message-ID: 264e69aed5a2fdd93ad555dff96daeabc5c35724.camel@cybertec.at
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On Thu, 2026-05-28 at 20:47 +0200, Joel Jacobson wrote:
> This patch implements a new SQL language feature, that we intent to
> submit as a Change Proposal to the WG 3 SQL committee for the next
> meeting in Stockholm in June. We would greatly appreciate any feedback
> from the community.

Your presentation at the pgconf.dev really convinced me that this is
a useful feature.

I had only one consideration:

> FROM orders o
> LEFT JOIN order_items oi FOR KEY (order_id) -> o (id)

In the spirit of looking more like SQL, how about replacing the
arrows with FROM and TO?

Either

a JOIN b FOR KEY (col1) TO (col2)

or, slightly more verbose and natural language-like:

a JOIN b FOR KEY FROM (col1) TO (col2)

And if the arrow points the other way,

a JOIN b FOR KEY (col1) FROM (col2)

or

a JOIN b FOR KEY TO (col1) FROM (col2)

Yours,
Laurenz Albe

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  • Key joins at 2026-05-28 18:47:50 from Joel Jacobson

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