From dev-return-37484-archive-asf-public=cust-asf.ponee.io@subversion.apache.org Fri Feb 16 02:07:43 2018 Return-Path: X-Original-To: archive-asf-public@cust-asf.ponee.io Delivered-To: archive-asf-public@cust-asf.ponee.io Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by mx-eu-01.ponee.io (Postfix) with SMTP id 4560B18064A for ; Fri, 16 Feb 2018 02:07:43 +0100 (CET) Received: (qmail 3541 invoked by uid 500); 16 Feb 2018 01:07:42 -0000 Mailing-List: contact dev-help@subversion.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Delivered-To: mailing list dev@subversion.apache.org Received: (qmail 3529 invoked by uid 99); 16 Feb 2018 01:07:42 -0000 Received: from mail-relay.apache.org (HELO mailrelay1-lw-us.apache.org) (207.244.88.152) by apache.org (qpsmtpd/0.29) with ESMTP; Fri, 16 Feb 2018 01:07:42 +0000 Received: from zulu.dev.digiverse.si (unknown [77.234.149.122]) by mailrelay1-lw-us.apache.org (ASF Mail Server at mailrelay1-lw-us.apache.org) with ESMTPSA id BFF71560 for ; Fri, 16 Feb 2018 01:07:40 +0000 (UTC) Subject: Re: Backward or forward deltas, backend, FSX To: dev@subversion.apache.org References: <808f4972-26b9-5e38-4ced-e71c5bd071c9@prolan-power.hu> <1518729061.2011543.1272308056.0E1748CF@webmail.messagingengine.com> From: =?UTF-8?Q?Branko_=c4=8cibej?= Organization: The Apache Software Foundation Message-ID: Date: Fri, 16 Feb 2018 02:07:38 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <1518729061.2011543.1272308056.0E1748CF@webmail.messagingengine.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-GB On 15.02.2018 22:11, Daniel Shahaf wrote: >> With say, 100000 revisions, when someone checks out the last revision: >> svn starts (would start, with the FSX backend) >> with the 30 years old, "fossile" ancient revision? (It would be case >> with the "FSFS-like way".) Which has nothing common >> with the recent revisions? And applies (at least) 17 deltas (patches)? >> Of which many deltas are very "heavy" (huge >> changings, complete rewritings)?.. I would marvel at that and do not >> understand the reasons.. > Note that when the delta is larger than the file it results in, > Subversion stores a compressed fulltext rather than a delta. Your > example of a file that has undergone multiple complete rewrites might > exercise that logic, which will shorten the walk. > > I'm not sure why you say "at least" 17 deltas. The default value of > max-linear-deltification (see fsfs.conf) is 16, meaning that no fulltext > will require 17 delta applications to produce. Another important thing to note is that the deltas are not applied in series; they are _combined_ in series and then the resulting combined delta is applied to the initial fulltext. Combining deltas is (in general) lot cheaper than applying them. -- Brane