From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by dcvr.yhbt.net (Postfix) with ESMTP id 6D15F1F5AE for ; Fri, 26 Jun 2020 14:40:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729265AbgFZOkI (ORCPT ); Fri, 26 Jun 2020 10:40:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725792AbgFZOkI (ORCPT ); Fri, 26 Jun 2020 10:40:08 -0400 Received: from mail-qv1-xf44.google.com (mail-qv1-xf44.google.com [IPv6:2607:f8b0:4864:20::f44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E9C2C03E979 for ; Fri, 26 Jun 2020 07:40:08 -0700 (PDT) Received: by mail-qv1-xf44.google.com with SMTP id g7so4561426qvx.11 for ; Fri, 26 Jun 2020 07:40:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=s6WUvJT2oBaN4ned/W3cVz6NmL7NwGCOJ4KPxcIA3Pw=; b=DA3HOjnf15tkvS73XkGGXpOpDCvCeqj7d6VTrE7b+x0olE+1D/Isgm+gG/aba8plNu iGc6Xp9hxHcrPIQ7qJLxRKx8k0YvwmyBU/rDTbk4vpmhbVLbwrw2QTD3BMX6mefsE5+a vhGw5iMkE3MY9BSSrM7oqtHvAdsK6FTAS3lTCrZYAXaNr8Fu8AendiqiUgRQgGcbagOA ucihAKpw5/KvElOHyZeIFUVqY0xlHLjKwmqQzh7GC2V5zAvUZVwSZ9PjH+Xvg1X+19S4 ZoVvRL9jFT+CqBHnYxTUCEfu90S4D2oDfjPHZqvpyJw9wDT5ajTwEQ6rtBpoUFILf/U0 Z8fQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=s6WUvJT2oBaN4ned/W3cVz6NmL7NwGCOJ4KPxcIA3Pw=; b=NYwkFmqOBZf1DY6xWNodeDNebf+NFK7sit8tJ/UHIDEuvPEohrOTYnAUnf9sqkCZCP mAUfekXRmrbBbRrzNY3cJqjWHG+rugLh0MV26sjgzEvX/v14K9DU8gAbpkL/3BYt1T7S IYG0y6QjMO5FciexlGJ2elS1CkGuTi/RfYy/BTCKP4TNZ1rM0TT4r1J4dmYPtD7fyr9b tyh/W1T8nwzSSdy4G604XHJHrECtqoxidFb8z1KxTNPeFxu26pMuUZsh2JW8QuJbcyI1 QHkk0Z4MARNb+Is0wzpJH2gYLvrDDBPQW6DiaNTjdiEHd903LhN/q05JYW9fCCAPZNl9 bBgA== X-Gm-Message-State: AOAM5309NCiSlJvs7PZ5Jm+5xakPV+KvlsVtS/aR+f8gmTgjqtL/ZfkQ YfO+z5SYgaCzDzOsYKG+z4y9XTJM92M= X-Google-Smtp-Source: ABdhPJyDAb1dmLVDEk5ORpgGe9wCKWDDQoo59zOeziILlgiYNZqULXXLh0vH+i/R8F+BDeWOElDv5Q== X-Received: by 2002:a0c:8284:: with SMTP id i4mr3337506qva.77.1593182407224; Fri, 26 Jun 2020 07:40:07 -0700 (PDT) Received: from [192.168.1.110] ([99.85.27.166]) by smtp.gmail.com with ESMTPSA id w1sm8661176qto.0.2020.06.26.07.40.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 Jun 2020 07:40:06 -0700 (PDT) Subject: Re: [RFC] Metadata vs Generation Data Chunk To: 10d99e37-8870-6401-d9aa-21a359b30835@gmail.com, jnareb@gmail.com Cc: git@vger.kernel.org References: <20200626134422.GA17537@Abhishek-Arch> From: Derrick Stolee Message-ID: <3bdbf490-a7ae-2351-9c82-6b19a577b641@gmail.com> Date: Fri, 26 Jun 2020 10:40:06 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.0 MIME-Version: 1.0 In-Reply-To: <20200626134422.GA17537@Abhishek-Arch> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On 6/26/2020 9:44 AM, Abhishek Kumar wrote: > On 22.06.2020 at 13:40, Jakub Narębski wrote: >> On 22.06.2020 at 11:34, Abhishek Kumar wrote: >> >>> One of the remaining pre-requisites for implementing generation number >>> v2 was distinguishing between corrected commit dates with monotonically >>> increasing offsets and topological level without incrementing generation >>> number version. >>> >>> Two approaches were proposed [1]: >>> 1. New chunk for commit data (generation data chunk, "GDAT") >>> 2. Metadata/versioning chunk >> >> Actually in [1] there was also proposed another distinct approach, >> namely to 'rename' the "CDAT" chunk to something else, like "CDA2" >> (or proposed here "GDAT"). >> >> If I read the code correctly, with old Git if one of required chunks >> is missing then Git would continue work as if commit-graph was not >> present -- as opposed to current handling of unknown commit-graph >> file format version number, where Git would stop working with an >> error message. >> > > Actually, v2.21.0 (and possibly others) segfault when they encounter a > commit-graph without CDAT chunk. Yes, the CDAT chunk is absolutely necessary. It also includes data such as the commit-date, root tree id, and parent information. > With this, I presume "CDAT Chunk Replaced With Another Chunk" is no > longer feasible? "Replace" was never on the table (in my mind). Instead, we can consider _adding_ a new chunk that contains the generation number v2 data. Thanks, -Stolee