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From: Frits Hoogland <[email protected]>
To: Andres Freund <[email protected]>
Cc: Laurenz Albe <[email protected]>
Cc: Aleksander Alekseev <[email protected]>
Cc: [email protected]
Subject: Re: The ability of postgres to determine loss of files of the main fork
Date: Wed, 1 Oct 2025 17:25:00 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <cbnna46p73gtyzbw22x67vuihcqmqwfbjgbzkdmrynovatvjlf@kwks4cei2jgh>
References: <[email protected]>
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	<[email protected]>
	<[email protected]>
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	<cbnna46p73gtyzbw22x67vuihcqmqwfbjgbzkdmrynovatvjlf@kwks4cei2jgh>


> On 1 Oct 2025, at 15:49, Andres Freund <[email protected]> wrote:
> 
> Hi,
> 
> On 2025-10-01 15:39:04 +0200, Laurenz Albe wrote:
>> On Wed, 2025-10-01 at 13:58 +0200, Frits Hoogland wrote:
>>> I am proposing the database to have the ability to detect when it has missing segments.
>> 
>> Just a random idea: one solution would be if each segment has a flag that indicates
>> if that is the last segment or not.  But that would break the on-disk storage format,
>> unless there is room left for an extra flag somewhere in the current layout.
> 
> It'd also make extensions / truncations more complicated. I rather doubt we're
> going there. Right now relation extension aren't WAL logged. While there might
> be reasons to change that, I don't think this is enough justification for
> doing so.
> 

What would be a achievable way of making postgres under the relation size?
How about a field in pg_class that keeps the final data page, so that the catalog
keeps the size, which then allows utilities and the database itself to understand how
many segments should exist?

> Greetings,
> 
> Andres

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