From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Rast Subject: Re: [GSoC] Designing a faster index format Date: Wed, 21 Mar 2012 13:51:10 +0100 Message-ID: <871uomrubl.fsf@thomas.inf.ethz.ch> References: <8D287169-1AD9-4586-BDBC-F820220328FC@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: Nguyen Thai Ngoc Duy , To: Thomas Gummerer X-From: git-owner@vger.kernel.org Wed Mar 21 13:51:20 2012 Return-path: Envelope-to: gcvg-git-2@plane.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1SAL0Y-0001Lw-Dm for gcvg-git-2@plane.gmane.org; Wed, 21 Mar 2012 13:51:18 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758582Ab2CUMvN (ORCPT ); Wed, 21 Mar 2012 08:51:13 -0400 Received: from edge10.ethz.ch ([82.130.75.186]:32147 "EHLO edge10.ethz.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758538Ab2CUMvM (ORCPT ); Wed, 21 Mar 2012 08:51:12 -0400 Received: from CAS22.d.ethz.ch (172.31.51.112) by edge10.ethz.ch (82.130.75.186) with Microsoft SMTP Server (TLS) id 14.1.355.2; Wed, 21 Mar 2012 13:51:09 +0100 Received: from thomas.inf.ethz.ch.ethz.ch (129.132.153.233) by CAS22.d.ethz.ch (172.31.51.112) with Microsoft SMTP Server (TLS) id 14.1.355.2; Wed, 21 Mar 2012 13:51:11 +0100 In-Reply-To: (Nguyen Thai Ngoc Duy's message of "Wed, 21 Mar 2012 17:34:15 +0700") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.3 (gnu/linux) X-Originating-IP: [129.132.153.233] Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: Nguyen Thai Ngoc Duy writes: > On Wed, Mar 21, 2012 at 4:22 PM, Thomas Gummerer wrote: >> >> On Mar 21, 2012, at 2:29 AM, Nguyen Thai Ngoc Duy wrote: >> >> However I got one more question, since I'm not yet really familiar with the >> code and internal structure of git, what exactly does the SHA1 over the >> index exactly achieve? Is it only for checking if the index is still correct >> for the next time it is used and has not been changed or is there a more >> important function of it? > > It makes sure the index is not corrupt (by disk faults for example). I > don't think it is used for anything else. Cheaper checksum can be used > if good enough for the index. See > http://thread.gmane.org/gmane.comp.version-control.git/190016 and the > following reply. Note that switching the checksum used already requires a backwards-incompatible change of the index format. If we are going to do that, I'm somewhat opposed to not also revising it along the lines sketched by Shawn (at least). See my reply to Elton Sky http://thread.gmane.org/gmane.comp.version-control.git/193550/focus=193571 for links to some threads you may want to look at. -- Thomas Rast trast@{inf,student}.ethz.ch