From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6BB12CD6130 for ; Mon, 9 Oct 2023 19:52:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378457AbjJITwS (ORCPT ); Mon, 9 Oct 2023 15:52:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1376628AbjJITwR (ORCPT ); Mon, 9 Oct 2023 15:52:17 -0400 Received: from pb-smtp2.pobox.com (pb-smtp2.pobox.com [64.147.108.71]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0FC1693 for ; Mon, 9 Oct 2023 12:52:16 -0700 (PDT) Received: from pb-smtp2.pobox.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 57BE51A1017; Mon, 9 Oct 2023 15:52:15 -0400 (EDT) (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=9g2SLIs+Nx2TrBfuVcTB5bahUxOO3wLY49Oh2Q LyU8k=; b=Kh2/80Zkwi8ZAXa0PrJ5T9ZOBTmXY9lMo+Ff3+2WqhF6dS9gUpDZ6C q/B9f5HvOhE8TktwLab2rNnQF0iQ0QXcG3grRZ1DIlssnXODMMhjzG1IcPZeC6+/ K/d5oJFz5Ts0XPwMRTRrqBHpKHBUcmw0E1pVoVqXrMqVhX5dOhv9o= Received: from pb-smtp2.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 4FCB51A1016; Mon, 9 Oct 2023 15:52:15 -0400 (EDT) (envelope-from junio@pobox.com) Received: from pobox.com (unknown [34.125.153.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp2.pobox.com (Postfix) with ESMTPSA id B77DE1A1015; Mon, 9 Oct 2023 15:52:14 -0400 (EDT) (envelope-from junio@pobox.com) From: Junio C Hamano To: Taylor Blau Cc: SZEDER =?utf-8?Q?G=C3=A1bor?= , Jonathan Tan , git@vger.kernel.org, Jeff King Subject: Re: [PATCH 07/15] commit-graph: new filter ver. that fixes murmur3 In-Reply-To: (Taylor Blau's message of "Mon, 9 Oct 2023 15:31:51 -0400") References: <20230830200218.GA5147@szeder.dev> <20230901205616.3572722-1-jonathantanmy@google.com> <20231008143523.GA18858@szeder.dev> Date: Mon, 09 Oct 2023 12:52:13 -0700 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Pobox-Relay-ID: 5825CBA0-66DD-11EE-B1CE-25B3960A682E-77302942!pb-smtp2.pobox.com Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Taylor Blau writes: > However, I am not entirely sure I agree with you that this is a "new" > issue. At least in the sense that Git (on 'master') does not currently > know how to deal with Bloom filters that have different settings across > commit-graph layers. > > IOW, you could produce this problem today using the test you wrote in > <20201015132147.GB24954@szeder.dev> using different values of the > GIT_BLOOM_SETTINGS environment variables as a proxy for different values > of the commitGraph.changedPathsVersion configuration variable introduced > in this series. > > So I think that this series makes it easier to fall into that trap, but > the trap itself is not new. I think a reasonable stopgap (which IIUC you > have suggested earlier) is to prevent writing a new commit-graph layer > with a different hash version than the previous layer. What we probably want more urgently than that stopgap is to perhaps teach the code pretend as if commit-graph did not exist when we detect multiple layers use different hash versions (or perhaps only use the base layer and ignore the rest as an anti-pessimization), to protect correctness first, no?