Re: Poor performance of git describe in big repos

From: Alex Bennée <kernel-hacker@bennee.com>
Date: May 31, 2013, 08:14 UTC
Message-ID: <CAJ-05NOEuxOVy7LFp_XRa_08G-Mj0x7q+RiR=u71-iyfOXpHow@mail.gmail.com>
In-Reply-To: <20130530193046.GG17475@serenity.lan>

On 30 May 2013 20:30, John Keeping <john@keeping.me.uk> wrote:

Show 12 quoted lines

> On Thu, May 30, 2013 at 06:21:55PM +0200, Thomas Rast wrote:
>> Alex Bennée <kernel-hacker@bennee.com> writes:
>>
>> > On 30 May 2013 16:33, Thomas Rast <trast@inf.ethz.ch> wrote:
>> >> Alex Bennée <kernel-hacker@bennee.com> writes:
> <snip>
>> > Will it be loading the blob for every commit it traverses or just ones that hit
>> > a tag? Why does it need to load the blob at all? Surely the commit
>> > tree state doesn't
>> > need to be walked down?
>>
>> No, my theory is that you tagged *the blobs*.  Git supports this.

Wait is this the difference between annotated and non-annotated tags? I thought a non-annotated just acted like references to a particular tree state?

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>
> You can see if that is the case by doing something like this:
>
>     eval $(git for-each-ref --shell --format '
>         test $(git cat-file -t %(objectname)^{}) = commit ||
>         echo %(refname);')
>
> That will print out the name of any ref that doesn't point at a
> commit.

Hmm that didn't seem to work. But looking at the output by hand I certainly have a mix of tags that are commits vs tags:

09:08 ajb@sloy/x86_64 [work.git] >git for-each-ref | grep "refs/tags"
| grep "commit" | wc -l
1345
09:12 ajb@sloy/x86_64 [work.git] >git for-each-ref | grep "refs/tags"
| grep -v "commit" | wc -l
66

Unfortunately I can't just delete those tags as they do refer to known releases which we obviously care about. If I delete the tags on my local repo and test for a speed increase can I re-create them as annotated tag objects?

-- 
Alex, homepage: http://www.bennee.com/~alex/