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From: Greg Sabino Mullane <[email protected]>
To: Lars Aksel Opsahl <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: PostgreSQL and a Catch-22 Issue related to dead rows
Date: Mon, 9 Dec 2024 08:35:20 -0500
Message-ID: <CAKAnmmL=_kuK2B6KtVpuCdta65MajTSvjQYSCdx=xhPLOW0shA@mail.gmail.com> (raw)
In-Reply-To: <AM7P189MB10281DCA1FD196A5610484B29D3C2@AM7P189MB1028.EURP189.PROD.OUTLOOK.COM>
References: <AM7P189MB10281DCA1FD196A5610484B29D3C2@AM7P189MB1028.EURP189.PROD.OUTLOOK.COM>

On Mon, Dec 9, 2024 at 6:03 AM Lars Aksel Opsahl <[email protected]>
wrote:

> In one case, we processed a total of 750 cells, with an overall runtime of
> 40 hours. However, one specific cell took over 12 hours to complete, most
> of which was spent on removing small areas by deleting edges in PostGIS
> Topology. The root cause of this delay is related to removal of dead rows.
>
Can you please expand exactly what you mean by "removal of dead rows" here,
and what the exact issue you are facing is?

> By introducing periodic COMMIT statements and VACUUM (FULL) operations
>
Vacfull is a pretty rough solution, and almost always not the correct tool
for the job, IMHO.

Yes there are very good reason for the way removal for dead rows work now,
> but is there any chance of adding an option when creating table to disable
> this behavior for instance for unlogged tables ?
>

It's still not clear exactly what the ask is here, but there is little
chance we would design an alternative MVCC system just to accommodate this
use case.

Cheers,
Greg

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