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help / color / mirror / Atom feedFrom: Mats Kindahl <mats.kindahl@gmail.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: japinli@hotmail.com
Cc: suryapoondla4@gmail.com
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: pg_rewind does not rewind diverging timelines
Date: Wed, 12 Aug 2026 07:05:07 +0200
Message-ID: <8cb012f7-1058-41ee-a727-90f3ecbecb58@gmail.com> (raw)
In-Reply-To: <20260601.153058.2271004477925758292.horikyota.ntt@gmail.com>
References: <SY7PR01MB10921E0F8383139EB27B33C11B6162@SY7PR01MB10921.ausprd01.prod.outlook.com>
<9ce0d2b9-7a41-4a8a-b299-da295bb4514f@gmail.com>
<SY7PR01MB10921F0B09B693C8D5149880EB6152@SY7PR01MB10921.ausprd01.prod.outlook.com>
<20260601.153058.2271004477925758292.horikyota.ntt@gmail.com>
On 6/1/26 08:30, Kyotaro Horiguchi wrote:
> Sorry, I only just noticed this thread.
>
> I may be missing something, but UUID feels somewhat heavyweight to me
> for this problem.
>
> I wonder whether strengthening the history-based matching would be
> sufficient instead. If timelines with the same TLI but different
> histories can be treated as distinct and pg_rewind continues walking
> the history chain until it finds a common ancestor, that seems like a
> fairly natural fit with the existing timeline model.
Unfortunately, I do not think that will work. For the normally
problematic case, the two competing TLIs will have the same history. I
added extra tests to support a divergence further back, but I find this
a rare case.
> UUIDs would certainly make identification straightforward, although
> they would also introduce longer identifiers that are a bit less
> convenient for humans to work with. My initial thought is that it may
> be worth exploring how far we can get with the existing history
> information before introducing a new identifier.
Well, although they are written to the file, the normal TLI is just an
extra defense, not a replacement for the TLI.
Best wishes,
Mats Kindahl
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Subject: Re: pg_rewind does not rewind diverging timelines
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