Feedback-ID: id4a34324:Fastmail
Date: Tue, 2 Sep 2025 19:54:07 -0400
From: Andres Freund <andres@anarazel.de>
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: Kirill Reshke <reshkekirill@gmail.com>,
	Andrey Borodin <x4mmm@yandex-team.ru>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	Robert Haas <robertmhaas@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>
Subject: Re: eliminate xl_heap_visible to reduce WAL (and eventually set VM
 on-access)
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Hi,

On 2025-09-02 19:11:01 -0400, Melanie Plageman wrote:
> From dd98177294011ee93cac122405516abd89f4e393 Mon Sep 17 00:00:00 2001
> From: Melanie Plageman <melanieplageman@gmail.com>
> Date: Wed, 27 Aug 2025 08:50:15 -0400
> Subject: [PATCH v8 01/22] Remove unneeded VM pin from VM replay

LGTM.


> From 7c5cb3edf89735eaa8bee9ca46111bd6c554720b Mon Sep 17 00:00:00 2001
> From: Melanie Plageman <melanieplageman@gmail.com>
> Date: Wed, 27 Aug 2025 10:07:29 -0400
> Subject: [PATCH v8 02/22] Add assert and log message to visibilitymap_set

LGTM.


> From 07f31099754636ec9dabf6cca06c33c4b19c230c Mon Sep 17 00:00:00 2001
> From: Melanie Plageman <melanieplageman@gmail.com>
> Date: Tue, 17 Jun 2025 17:22:10 -0400
> Subject: [PATCH v8 03/22] Eliminate xl_heap_visible in COPY FREEZE
>
> Instead of emitting a separate WAL record for setting the VM bits in
> xl_heap_visible, specify the changes to make to the VM block in the
> xl_heap_multi_insert record instead.
>
> Author: Melanie Plageman <melanieplageman@gmail.com>
> Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
> Discussion: https://postgr.es/m/flat/CAAKRu_ZMw6Npd_qm2KM%2BFwQ3cMOMx1Dh3VMhp8-V7SOLxdK9-g%40mail.gmail.com


> +		/*
> +		 * If we're only adding already frozen rows to a previously empty
> +		 * page, mark it as all-frozen and update the visibility map. We're
> +		 * already holding a pin on the vmbuffer.
> +		 */
>  		else if (all_frozen_set)
> +		{
> +			Assert(visibilitymap_pin_ok(BufferGetBlockNumber(buffer), vmbuffer));
>  			PageSetAllVisible(page);
> +			LockBuffer(vmbuffer, BUFFER_LOCK_EXCLUSIVE);
> +			visibilitymap_set_vmbyte(relation,
> +									 BufferGetBlockNumber(buffer),
> +									 vmbuffer,
> +									 VISIBILITYMAP_ALL_VISIBLE |
> +									 VISIBILITYMAP_ALL_FROZEN);
> +		}