From: Michael J Gruber <git@drmicha.warpmail.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: Marat Radchenko <marat@slonopotamus.org>, git@vger.kernel.org
Subject: Re: What's the difference between `git show branch:file | diff -u - file` vs `git diff branch file`?
Date: Tue, 23 Aug 2011 22:07:43 +0200 [thread overview]
Message-ID: <4E54088F.7050700@drmicha.warpmail.net> (raw)
In-Reply-To: <7vk4a4rqvb.fsf@alter.siamese.dyndns.org>
Junio C Hamano venit, vidit, dixit 23.08.2011 19:15:
> Michael J Gruber <git@drmicha.warpmail.net> writes:
>
>> Marat Radchenko venit, vidit, dixit 23.08.2011 12:52:
>>>> Is that a very large tree or a very slow file system?
>>> Tree is large (500k files), file system is irrelevant since all time is spend on CPU.
>>>
>>>> Do we enumerate all
>>>> differing files and only then limit diff output by path??
>>>
>>> Dunno, that's why I am asking why it is so slow.
>>
>> Well, we have to read the full tree before diffing.
>
> Not necessarily, especially when pathspec is given like the original post,
> i.e. "git diff $tree_ish -- $path". We would need to open tree objects
> that lead to the leaf of the $path and a blob, but other objects won't be
> needed.
I meant: The way "git diff" is now, it does that.
>
> The default diff backend tries to come up with minimal changes by spending
> extra cycles, so it is not so surprising if the file compared is large-ish
> and/or has very many similar lines in itself (in which case there are many
> potential matching line pairs between the preimage and the postimage to be
> examined to produce a minimal diff).
But the file in this case is not that large, and "git diff" spends 30s!
Michael
next prev parent reply other threads:[~2011-08-23 20:07 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-23 7:25 What's the difference between `git show branch:file | diff -u - file` vs `git diff branch file`? Marat Radchenko
2011-08-23 10:03 ` Michael J Gruber
2011-08-23 10:52 ` Marat Radchenko
2011-08-23 15:20 ` Michael Witten
2011-08-23 15:34 ` Michael J Gruber
2011-08-23 16:45 ` Marat Radchenko
2011-08-23 17:15 ` Junio C Hamano
2011-08-23 18:21 ` Marat Radchenko
2011-08-23 20:07 ` Michael J Gruber [this message]
2011-08-25 16:09 ` Marat Radchenko
2011-08-25 21:10 ` Junio C Hamano
2011-08-26 9:43 ` Marat Radchenko
2011-08-29 7:41 ` Nguyen Thai Ngoc Duy
2011-08-29 14:48 ` Marat Radchenko
2011-08-29 16:09 ` Nguyen Thai Ngoc Duy
2011-08-29 17:18 ` Junio C Hamano
2011-08-29 20:42 ` Junio C Hamano
2011-08-29 20:50 ` Junio C Hamano
2011-08-29 21:09 ` Junio C Hamano
2011-08-29 21:33 ` [PATCH 0/3] Un-pessimize "diff-index $commit -- $pathspec" Junio C Hamano
2011-08-29 21:33 ` [PATCH 1/3] traverse_trees(): allow pruning with pathspec Junio C Hamano
2011-08-30 12:53 ` Nguyen Thai Ngoc Duy
2011-08-30 17:44 ` Junio C Hamano
2011-08-31 1:35 ` Nguyen Thai Ngoc Duy
2011-10-09 15:39 ` Michael Haggerty
2011-10-09 21:35 ` Nguyen Thai Ngoc Duy
2011-10-10 4:42 ` Michael Haggerty
2011-08-29 21:33 ` [PATCH 2/3] unpack-trees: " Junio C Hamano
2011-08-30 13:03 ` Nguyen Thai Ngoc Duy
2011-08-30 17:32 ` Junio C Hamano
2011-08-30 15:24 ` David Michael Barr
2011-08-29 21:33 ` [PATCH 3/3] diff-index: pass pathspec down to unpack-trees machinery Junio C Hamano
2012-01-11 6:31 ` Jonathan Nieder
2012-01-11 8:05 ` Junio C Hamano
2012-01-11 12:33 ` Nguyen Thai Ngoc Duy
2012-01-11 12:47 ` Nguyen Thai Ngoc Duy
2012-01-11 20:40 ` Junio C Hamano
2012-01-12 4:09 ` [PATCH] tree_entry_interesting: make recursive mode default Nguyễn Thái Ngọc Duy
2012-01-12 5:04 ` Junio C Hamano
2012-01-12 5:44 ` Nguyen Thai Ngoc Duy
2012-01-14 9:23 ` [PATCH v2 1/2] Document limited recursion pathspec matching with wildcards Nguyễn Thái Ngọc Duy
2012-01-14 9:23 ` [PATCH v2 2/2] tree_entry_interesting: make recursive mode default Nguyễn Thái Ngọc Duy
2012-01-15 3:12 ` Junio C Hamano
2012-01-15 10:03 ` Nguyen Thai Ngoc Duy
2012-01-16 22:15 ` Junio C Hamano
2012-01-18 8:59 ` Nguyen Thai Ngoc Duy
2012-01-15 2:38 ` [PATCH v2 1/2] Document limited recursion pathspec matching with wildcards Junio C Hamano
2012-01-15 9:48 ` Nguyen Thai Ngoc Duy
2011-08-29 21:56 ` [PATCH 0/3] Un-pessimize "diff-index $commit -- $pathspec" Linus Torvalds
2011-08-29 22:05 ` Junio C Hamano
2011-08-29 22:11 ` Linus Torvalds
2011-08-29 23:42 ` Junio C Hamano
2011-08-30 6:16 ` Marat Radchenko
2011-08-31 0:18 ` Junio C Hamano
2011-08-30 10:04 ` Michael J Gruber
2011-08-30 17:03 ` Junio C Hamano
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