From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-2.9 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, FROM_EXCESS_BASE64,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI shortcircuit=no autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 4EB7D1F453 for ; Wed, 31 Oct 2018 12:54:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729184AbeJaVwr (ORCPT ); Wed, 31 Oct 2018 17:52:47 -0400 Received: from mail-ed1-f47.google.com ([209.85.208.47]:35585 "EHLO mail-ed1-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728930AbeJaVwr (ORCPT ); Wed, 31 Oct 2018 17:52:47 -0400 Received: by mail-ed1-f47.google.com with SMTP id d6-v6so5423832edi.2 for ; Wed, 31 Oct 2018 05:54:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:references:user-agent:in-reply-to:date :message-id:mime-version; bh=x/MQZnxK0nbcGWQpSP09VvRlE784aN4Awfbgu4LrGsw=; b=qAMdEA4a9/h8SiW4IZzWaR7ZXAazzOxNp5CCN7UbamnNmOC4mIG4YW+xZ42MMRl4Nr 87Hugl7aQoKeaIsAhfNwguIVIyWWCSU7fAO3M2NP2dFS2iKK4JADmdDWFziqxn5t6Zzr s7B0iUMAKowrgmh/G/L5vH7mXC3GdAnL5iqH2fXiYdIsAPYa8AK+Udq2EyT2kCagVV2L 47lNX+EqaMGpPnL3UbsURhD/eoDC2x3NTRYkaY7oKYAbI8MIvlCH9UaTZz2QpPT2aos4 2ypou3HzIWMKCc1EtMlETMorOPtxVo/0fPDIIIApMlQUt+t6kU258svXQwE4u4yXZO+6 8cnw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:references:user-agent :in-reply-to:date:message-id:mime-version; bh=x/MQZnxK0nbcGWQpSP09VvRlE784aN4Awfbgu4LrGsw=; b=L7pAqx8Ce76Xb5XJWJGaSgB7FFOhwyx6t+GicrGjeSofxV9mPflTnWX9WpUWfkqoZ5 7z5RdzvyPy4eD7khlm9DeZrH7edK5zRJ3D2DtyARedZlQNcwkl14JmQGXacr2idZh31k P3d8uNJQvImTQyEunlyPyMEZKErMohxD5FviqghPkODVNRcIpXLcjNkZ3Z8D40czKy3j 5ocMTGOnr3Bdwk2LVeCBBXJORrg6nGhJq5esu1/yl+ls0Xmm4Z2q5uG9+8QBa4i/l8OM u7B3Ki3/Ev3EYVcRiTp4oUHOPdXXG0S4wTteF3s7ah6ZvjRLkbAk2pE5g91BubgFOKUp +LMg== X-Gm-Message-State: AGRZ1gLg9VVaMKdCfYNSDCX1TQIJj0we9WQ4TufvBrFGwS6czokeUC7C W7Vk5WOy5ZrGRSIy8Kp2sB0= X-Google-Smtp-Source: AJdET5dX1NuYuuF+zfR/3LzO3h2Uqhzsd8g3lOS8cuUctORWKHm2Kn772v5qMHBZ8+BLf2UJ1YdiWA== X-Received: by 2002:a17:906:25d3:: with SMTP id n19-v6mr1423094ejb.191.1540990491557; Wed, 31 Oct 2018 05:54:51 -0700 (PDT) Received: from evledraar (223-81-146-85.ftth.glasoperator.nl. [85.146.81.223]) by smtp.gmail.com with ESMTPSA id i5-v6sm432116edi.29.2018.10.31.05.54.50 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 31 Oct 2018 05:54:50 -0700 (PDT) From: =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason To: Junio C Hamano Cc: Derrick Stolee , Git List , Jeff King , =?utf-8?Q?Jakub_Nar=C4=99bski?= , Derrick Stolee Subject: Re: [RFC] Generation Number v2 References: <6367e30a-1b3a-4fe9-611b-d931f51effef@gmail.com> User-agent: Debian GNU/Linux testing (buster); Emacs 25.2.2; mu4e 1.1.0 In-reply-to: Date: Wed, 31 Oct 2018 13:54:48 +0100 Message-ID: <875zxil1if.fsf@evledraar.gmail.com> MIME-Version: 1.0 Content-Type: text/plain Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Tue, Oct 30 2018, Junio C Hamano wrote: > Derrick Stolee writes: >> In contrast, maximum generation numbers and corrected commit >> dates both performed quite well. They are frequently the top >> two performing indexes, and rarely significantly different. >> >> The trade-off here now seems to be: which _property_ is more important, >> locally-computable or backwards-compatible? > > Nice summary. > > As I already said, I personally do not think being compatible with > currently deployed clients is important at all (primarily because I > still consider the whole thing experimental), and there is a clear > way forward once we correct the mistake of not having a version > number in the file format that tells the updated clients to ignore > the generation numbers. For longer term viability, we should pick > something that is immutable, reproducible, computable with minimum > input---all of which would lead to being incrementally computable, I > would think. I think it depends on what we mean by backwards compatibility. None of our docs are saying this is experimental right now, just that it's opt-in like so many other git-config(1) options. So if we mean breaking backwards compatibility in that we'll write a new file or clobber the existing one with a version older clients can't use as an optimization, fine. But it would be bad to produce a hard error on older clients, but avoiding that seems as easy as just creating a "commit-graph2" file in .git/objects/info/.