Re: [HACKERS] GSoC 2017: Foreign Key Arrays

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Stefan Keller <sfkeller(at)gmail(dot)com>
Cc: Mark Rofail <markm(dot)rofail(at)gmail(dot)com>, Daniel Gustafsson <daniel(at)yesql(dot)se>, vignesh C <vignesh21(at)gmail(dot)com>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Andreas Karlsson <andreas(at)proxel(dot)se>, David Steele <david(at)pgmasters(dot)net>, Erik Rijkers <er(at)xs4all(dot)nl>, Hans-Jürgen Schönig <hs(at)cybertec(dot)at>, Joel Jacobson <joel(at)compiler(dot)org>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Robert Haas <robertmhaas(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Zhihong Yu <zyu(at)yugabyte(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] GSoC 2017: Foreign Key Arrays
Date: 2021-10-05 19:15:43
Message-ID: 202110051915.agicatxbn36k@alvherre.pgsql
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Hi Stefan,

On 2021-Oct-03, Stefan Keller wrote:

> Just for my understanding - and perhaps as input for the documentation of this:
> Are Foreign Key Arrays a means to implement "Generic Foreign Keys" as
> in Oracle [1] and Django [2], and of "Polymorphic Associations" as
> they call this in Ruby on Rails?

No -- at least as far as I was able to understand the pages you linked to.

It's intended for array elements of one column to reference values in a
scalar column. These are always specific columns, not "generic" or
"polymorphic" (which I understand to mean one of several possible


Álvaro Herrera 39°49'30"S 73°17'W —

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