Re: Fix RETURNING side effects for FOR PORTION OF leftover rows

From: Paul A Jungwirth <pj(at)illuminatedcomputing(dot)com>
To: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>
Cc: Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Fix RETURNING side effects for FOR PORTION OF leftover rows
Date: 2026-07-20 16:21:06
Message-ID: CA+renyXrMqiiNRWAA-pXj8peHRSP7RnT6PyiQ0gmuHK6i5gdkg@mail.gmail.com
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On Mon, Jul 20, 2026 at 6:17 AM Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com> wrote:
>
> Okay. We cannot simply check node->forPortionOf to bypass RETURNING processing, because an FPO update on a partitioned table may move a row to a different partition. In that case, ExecInsert() is also called to insert the row into the new partition.
>
> However, in that case, mtstate->operation is still CMD_UPDATE, while for leftover rows, mtstate->operation is temporarily changed to CMD_INSERT. So we can check both node->forPortionOf and mtstate->operation.
>
> PFA v2 with the new implementation. I tried to run check-world and it passed.

Nice catch. I took a look at the v2 patch. It looks like a good fix to
me. I'm happy that we're testing cross-partition updates as well.
Thanks for the quick fix!

Yours,

--
Paul ~{:-)
pj(at)illuminatedcomputing(dot)com

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