| From: | Vik Fearing <vik(at)postgresfriends(dot)org> |
|---|---|
| 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 |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| 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
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Vik Fearing | 2023-09-01 22:41:13 | Re: SQL:2011 application time |
| Previous Message | Jeff Davis | 2023-09-01 21:27:07 | Re: sandboxing untrusted code |