Feedback-ID: ie3de48e3:Fastmail
Date: Thu, 11 Dec 2025 21:04:15 +0100
From: =?utf-8?Q?=C3=81lvaro?= Herrera <alvherre@kurilemu.de>
To: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
Cc: Alexander Lakhin <exclusion@gmail.com>,
	Michael Paquier <michael@paquier.xyz>, Noah Misch <noah@leadboat.com>,
	PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Issues with ON CONFLICT UPDATE and REINDEX CONCURRENTLY
Message-ID: <202512111958.6ymanstmexrk@alvherre.pgsql>
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On 2025-Dec-09, Mihail Nikalayeu wrote:

> Hello!
> 
> After some investigation I ended up with a much simpler fix.
> It is self-explanatory in code and a commit message.

Yeah, that makes sense.  It's what I was trying to say in
https://postgr.es/m/202512072050.hcyysny65ugj@alvherre.pgsql
Pushed your patch, thanks.

I still wonder if it's possible to break things by doing something like

CREATE TABLE pt (a int) PARTITION BY LISt (a);
CREATE TABLE p1 PARTITION OF pt FOR VALUES IN (1);
CREATE TABLE p2 PARTITION OF pt FOR VALUES IN (2);
CREATE UNIQUE INDEX pti ON ONLY pt (a);
CREATE UNIQUE INDEX p1i ON p1 (a);
CREATE UNIQUE INDEX p2i ON p2 (a);
ALTER INDEX pti ATTACH PARTITION p1i;

and then do the
  INSERT INTO pt VALUES (1) ON CONFLICT (a) DO NOTHING;
dance concurrently with
  ALTER INDEX pti ATTACH PARTITION p2i;

This would be a much smaller problem than the already fixed ones though,
I think.

Thanks!

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Learn about compilers. Then everything looks like either a compiler or
a database, and now you have two problems but one of them is fun."
            https://twitter.com/thingskatedid/status/1456027786158776329