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From: Junio C Hamano <junkio@cox.net>
To: Jakub Narebski <jnareb@gmail.com>
Cc: git@vger.kernel.org, mercurial@selenic.com
Subject: Re: newbie questions about git design and features (some wrt hg)
Date: Wed, 31 Jan 2007 12:01:15 -0800	[thread overview]
Message-ID: <7vabzzvud0.fsf@assigned-by-dhcp.cox.net> (raw)
In-Reply-To: <eppshi$1l4$1@sea.gmane.org> (Jakub Narebski's message of "Wed, 31 Jan 2007 11:56:01 +0100")

Jakub Narebski <jnareb@gmail.com> writes:

> Theodore Tso wrote:
>> 
>> To be fair hg modifies files using O_APPEND only.  That isn't quite as
>> safe as "only creating new files", but it is relatively safe.
>
> From (libc.info):
>  -- Macro: int O_APPEND
>  ...
> I don't quote understand how that would help hg (Mercurial) to have
> operations like commit, pull/fetch or push atomic, i.e. all or nothing.

If I remember correctly, thanks to their log-like file format,
they can rely on O_APPEND to do the right thing when growing,
and aborting the current transaction is just a truncate away (or
a set of truncates on the files appended in the transaction, if
hg touches more than one log-like file but I do not know if hg
uses only one file or more than one).  That's one of the things
I found clean and beautiful (from theoretical point of view, at
least) in their design.  I do not think O_APPEND is not used to
control concurrent operations.

  reply	other threads:[~2007-01-31 20:01 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-30 16:20 newbie questions about git design and features (some wrt hg) Mike Coleman
2007-01-30 16:41 ` Johannes Schindelin
2007-01-30 16:55 ` Shawn O. Pearce
2007-01-31  1:55   ` Theodore Tso
2007-01-31 10:56     ` Jakub Narebski
2007-01-31 20:01       ` Junio C Hamano [this message]
2007-01-31 22:25       ` Matt Mackall
2007-01-31 23:58         ` Jakub Narebski
2007-02-01  0:34           ` Matt Mackall
2007-02-01  0:57             ` Jakub Narebski
2007-02-01  7:59               ` Simon 'corecode' Schubert
2007-02-01 10:09                 ` Johannes Schindelin
2007-02-01 10:15                   ` Simon 'corecode' Schubert
2007-02-01 10:49                     ` Johannes Schindelin
2007-02-01 16:28                     ` Linus Torvalds
2007-02-01 19:36                       ` Eric Wong
2007-02-01 21:13                         ` Linus Torvalds
2007-02-02  9:55             ` Jakub Narebski
2007-02-02 13:51               ` Simon 'corecode' Schubert
2007-02-02 14:23                 ` Jakub Narebski
2007-02-02 15:02                   ` Shawn O. Pearce
2007-02-02 15:38               ` Mark Wooding
2007-02-02 16:09                 ` Jakub Narebski
2007-02-02 16:42                   ` Linus Torvalds
2007-02-02 16:59                     ` Jakub Narebski
2007-02-02 17:11                       ` Linus Torvalds
2007-02-02 17:59                     ` Brendan Cully
2007-02-02 18:19                       ` Jakub Narebski
2007-02-02 19:28                         ` Brendan Cully
2007-02-02 18:27                       ` Giorgos Keramidas
2007-02-02 19:01                         ` Linus Torvalds
2007-02-03 21:20                           ` Giorgos Keramidas
2007-02-03 21:37                             ` Matthias Kestenholz
2007-02-03 21:41                             ` Linus Torvalds
2007-02-03 21:45                             ` Jakub Narebski
2007-02-02 18:32                       ` Linus Torvalds
2007-02-02 19:26                         ` Brendan Cully
2007-02-02 19:42                           ` Linus Torvalds
2007-02-02 19:55                             ` Brendan Cully
2007-02-02 20:15                               ` Jakub Narebski
2007-02-02 20:21                               ` Linus Torvalds
2007-02-02 16:03               ` Matt Mackall
2007-02-02 17:18                 ` Jakub Narebski
2007-02-02 17:37                   ` Matt Mackall
2007-02-02 18:44                     ` Jakub Narebski
2007-02-02 19:56                       ` Jakub Narebski
2007-02-03 20:06                         ` Brendan Cully
2007-02-03 20:55                           ` Jakub Narebski
2007-02-03 21:00                             ` Jakub Narebski
2007-01-30 17:44 ` Jakub Narebski
2007-01-30 18:06 ` Linus Torvalds
2007-01-30 19:37   ` Linus Torvalds
2007-01-30 18:11 ` Junio C Hamano
2007-01-31  3:38   ` Mike Coleman
2007-01-31  4:35     ` Linus Torvalds
2007-01-31  4:57       ` Junio C Hamano
2007-01-31 16:22         ` Linus Torvalds
2007-01-31 16:41           ` Johannes Schindelin
2007-01-31  7:11       ` Mike Coleman
2007-01-31 15:03     ` Nicolas Pitre
2007-01-31 16:58       ` Mike Coleman

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