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From: Kirill Reshke <reshkekirill@gmail.com>
Date: Wed, 7 Jan 2026 10:55:03 +0500
Message-ID: <CALdSSPjuUb-kMnwjTNWXFBvBUtnu4ckOC5bOEwEWu+_mTVL3dg@mail.gmail.com>
Subject: Re: eliminate xl_heap_visible to reduce WAL (and eventually set VM on-access)
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: Andrey Borodin <x4mmm@yandex-team.ru>, Chao Li <li.evan.chao@gmail.com>, 
	Xuneng Zhou <xunengzhou@gmail.com>, Andres Freund <andres@anarazel.de>, 
	Robert Haas <robertmhaas@gmail.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Heikki Linnakangas <hlinnaka@iki.fi>
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On Tue, 6 Jan 2026 at 22:32, Melanie Plageman <melanieplageman@gmail.com> wrote:
>
> Ah, yes, I forgot to remove that when I removed the old
> visibilitymap_set() and made visibilitymap_set_vmbits() into
> visiblitymap_set(). Done in v33.
>
> - Melanie

I think 0001-0003 and 0009-0010 are ready.

> That test creates a table, inserts tuples, accesses one page, deletes
all the data, accesses a single page again (until the table is
vacuumed, the pages will still be there and have to be scanned even
though the data is deleted). The first time we set the VM on-access,
we have to extend the VM. That VM access is an extend and not a hit.
Once we set pd_prune_xid on the page, the extend happens during the
first access (before the delete), so when we access the VM after the
delete step, that is counted as a hit and we end up with more hits in
the stats.


Good

-- 
Best regards,
Kirill Reshke