From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pb-smtp1.pobox.com (pb-smtp1.pobox.com [64.147.108.70]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A912D1D523 for ; Tue, 16 Jan 2024 23:42:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=64.147.108.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705448563; cv=none; b=IIfCKqIo4O8sEx1coIWKGARDI9w7JJ/BNEirVheFgqu4nrzReS+xRxTFDndU1vnnX+eVib9bAwW//KmG46+odb98e065eoq11lMmQcIQu9WA2bCH3Iw8K3gqkIHLRGJhD9nRsv0l3vcZhAgAD2gXY7F/mbgvB1KttoPmyyHmrmc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705448563; c=relaxed/simple; bh=C9IsWCryPs8CmEXFuSEQceKiM4ZGx5yYJLDH0+NgD18=; h=Received:DKIM-Signature:Received:Received:From:To:Cc:Subject: In-Reply-To:References:Date:Message-ID:User-Agent:MIME-Version: Content-Type:X-Pobox-Relay-ID; b=SkEjPbdKpFAlKYb7KtBxsY1Re8KZxs18ZVnmRBD75qnsavHwsq/z1x1ZJIKkg01a13UiSPPdnZRIkjXpIFDp3LNAhaOnlNNoixQSSE2id5Z/AJ6BRXLCJF1yRxjGf8bmekAnryR9yUd8t76krnLMHqqe8/QxwRqQZKKk4xRDI1o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=pobox.com; spf=pass smtp.mailfrom=pobox.com; dkim=pass (1024-bit key) header.d=pobox.com header.i=@pobox.com header.b=XuzsJHOC; arc=none smtp.client-ip=64.147.108.70 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=pobox.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pobox.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=pobox.com header.i=@pobox.com header.b="XuzsJHOC" Received: from pb-smtp1.pobox.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 71DCA1B8890; Tue, 16 Jan 2024 18:42:40 -0500 (EST) (envelope-from junio@pobox.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed; d=pobox.com; h=from:to:cc :subject:in-reply-to:references:date:message-id:mime-version :content-type; s=sasl; bh=C9IsWCryPs8CmEXFuSEQceKiM4ZGx5yYJLDH0+ NgD18=; b=XuzsJHOC0pp0Pdzmqxs8NtJ+gewQOv5s8smRzkPfGlvvHmRTtSgbSU QV+ZlAXYSijnXV0IOeCDy5Ia785K2B1Qtqs2VF5Vk01M/GFYh5aC0xYZB9wZgRWA xY4XuJ9ktNeYZQ1gub5pwtB85w6k30pAMVjZ/ecnGGZijfbkCGXLI= Received: from pb-smtp1.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 69EC01B888F; Tue, 16 Jan 2024 18:42:40 -0500 (EST) (envelope-from junio@pobox.com) Received: from pobox.com (unknown [34.125.200.93]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp1.pobox.com (Postfix) with ESMTPSA id D4D811B888D; Tue, 16 Jan 2024 18:42:39 -0500 (EST) (envelope-from junio@pobox.com) From: Junio C Hamano To: Taylor Blau Cc: SZEDER =?utf-8?Q?G=C3=A1bor?= , git@vger.kernel.org Subject: Re: What's cooking in git.git (Jan 2024, #01; Tue, 2) In-Reply-To: (Taylor Blau's message of "Tue, 16 Jan 2024 18:31:19 -0500") References: <20240113183544.GA3000857@szeder.dev> <20240113225157.GD3000857@szeder.dev> Date: Tue, 16 Jan 2024 15:42:38 -0800 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Pobox-Relay-ID: EF73C9B0-B4C8-11EE-A2DF-78DCEB2EC81B-77302942!pb-smtp1.pobox.com Taylor Blau writes: >> A big red button solution to avoid this would be to uprev the >> repository format version once you start writing v2 Bloom filters >> anywhere in the layers. That way, existing Git clients would not be >> able to touch it. I do not know if the cure is more severe than the >> disease in that case, though. > > I tend to think that in this case the cure is probably worse than the > disease. I expect it to be extremely rare that a user would upgrade to a > modern version of Git, write commit-graphs, then downgrade, and try to > write more commit-graphs. But then the big red button solution would rarely misfire for users because they will not downgrade (and see "gee, I now need to stick to the newer version"), no? I am not seriously suggesting to do this, but I am not sure if documenting "don't do this because you'll break your repository" is sufficient. >> In any case, at least, we should be able to prepare the code that we >> teach to grok v2 today so that they do not trigger the same segfault >> when they see a commit graph layer containing v3 Bloom filters (or >> later). Then we won't have to have the same conversation when we >> somehow need to update Bloom filters again. > > This series should accomplish that by loading the Bloom chunk > unconditionally, and only reading its filters when they match the > given hash_version. Good.