From: | Vik Fearing <vik(at)postgresfriends(dot)org> |
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To: | Melanie Plageman <melanieplageman(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Why doesn't Vacuum FULL update the VM |
Date: | 2023-09-01 21:48:22 |
Message-ID: | da7a8a3c-f305-5033-13fa-a3f960fcb0ce@postgresfriends.org |
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Lists: | pgsql-hackers |
On 9/1/23 21:34, Melanie Plageman wrote:
> Hi,
>
> I noticed that VACUUM FULL actually does freeze the tuples in the
> rewritten table (heap_freeze_tuple()) but then it doesn't mark them
> all visible or all frozen in the visibility map. I don't understand
> why. It seems like it would save us future work.
I have often wondered this as well, but obviously I haven't done
anything about it.
> I don't see why the visibility map shouldn't be updated so that all of
> the pages show all visible and all frozen for this relation after the
> vacuum full.
It cannot just blindly mark everything all visible and all frozen
because it will copy over dead tuples that concurrent transactions are
still allowed to see.
--
Vik Fearing
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