Re: [PATCH 5.5/22] Add documentation for the index api

From: Duy Nguyen <pclouds@gmail.com>
To: Thomas Gummerer <t.gummerer@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
	Thomas Rast <trast@inf.ethz.ch>,
	Michael Haggerty <mhagger@alum.mit.edu>,
	Junio C Hamano <gitster@pobox.com>,
	Robin Rosenberg <robin.rosenberg@dewire.com>
Subject: Re: [PATCH 5.5/22] Add documentation for the index api
Date: Thu, 11 Jul 2013 18:42:06 +0700	[thread overview]
Message-ID: <CACsJy8DNQ5Sr4a7PZMX4G-pf+fHqR398b3mncCZtQ-BBBpD+RQ@mail.gmail.com> (raw)
In-Reply-To: <87ppupcp19.fsf@gmail.com>

On Thu, Jul 11, 2013 at 6:30 PM, Thomas Gummerer <t.gummerer@gmail.com> wrote:
> Duy Nguyen <pclouds@gmail.com> writes:
>
>> On Wed, Jul 10, 2013 at 3:10 AM, Thomas Gummerer <t.gummerer@gmail.com> wrote:
>>>> If you happen to know that certain entries match the given pathspec,
>>>> you could help the caller avoid match_pathspec'ing again by set a bit
>>>> in ce_flags.
>>>
>>> I currently don't know which entries do match the pathspec from just
>>> reading the index file, additional calls would be needed.  I don't think
>>> that would be worth the overhead.
>>
>> Yeah I now see that you select what to load in v5 with the adjusted
>> pathspec, not the input pathspec. Originally I thought you match the
>> input pathspec against every file entry in the index :P Your adjusted
>> pathspec looks like what common_prefix is for. It's cheaper than
>> creating adjusted_pathspec from match_pathspec and reduces loading in
>> major cases, where glob is not used.
>>
>> Still, creating an adjusted pathspec this way looks iffy. You need to
>> understand pathspec in order to strip the filename part out to match
>> the directory match only. An alternative is use
>> tree_entry_interesting. It goes along well with tree traversal and can
>> be used to match directories with original pathspec. Once you see it
>> matches an entry in a directory, you could skip matching the rest of
>> the files and load the whole directory. read_index_filtered_v5 and
>> read_entries may need some tweaking though. I'll try it and post a
>> patch later if I succeed.
>
> Hrm, I played around a bit with this idea, but I couldn't figure out how
> to make it work.  For it to work we would still have to load some
> entries in a directory at least?  Or is there a way to match the
> directories, which I just haven't figured out yet?

Yes you have to load some entries first. Even if a directory does not
match, we only know until at least the first file in the directory. OK
there might be problems because tree_entry_interesting expects all
entries in a directory to be memcmp sorted, without trailing slash for
subdirectories. I need to check again if v5 sort order is compatible..
--
Duy