Re: [PATCH 1/3] Lazily open pack index files on demand

From: Dana How <danahow@gmail.com>
Date: May 27, 2007, 04:31 UTC
Message-ID: <56b7f5510705262131g2d4186a0q605abbcea624d42d@mail.gmail.com>
In-Reply-To: <alpine.LFD.0.99.0705262223540.3366@xanadu.home>

On 5/26/07, Nicolas Pitre <nico@cam.org> wrote:

Show 12 quoted lines

> On Sat, 26 May 2007, Dana How wrote:
> > (1) git-repack -a -d repacks everything on each call.  You would need:
> > (1a) Rewrite builtin-pack-objects.c so only the object_ix hash
> >       accesses the "objects" array directly, everything else
> >       goes through a pointer table.
> > (1b) Sort the new pointer table by object type,  in order
> >       tag -> commit -> tree -> nice blob -> naughty blob.
> >      The sort is stable so the order within each group is unchanged.
>
> Because commit objects are so fundamental to many graph operations they
> are already all packed together.  But tree and blob objects are
> intermixed for the reason stated above.

I noticed that all the commits were together and wondered if that was deliberate.

> The naughty blob is a really special category and I think they should be
> treated as such. Therefore I don't think the common/normal case should
> be impacted with a generic change for something that is still a special
> case.

This argument makes sense.

Show 5 quoted lines

> In other words, I think the naughty blob could simply be recognized as
> such and be referenced in a special list instead of being written out
> initially.  Then when everything is believed to be written, the special
> list can be walked to force write those naughty blob at last.  No need
> to modify the current object order.

This works as long as a naughty blob can't be a delta base for a nice blob (causing it to be pushed out early by the recursion in write_one()). I think that's a reasonable and understandable restriction.

Thanks,

-- 
Dana L. How  danahow@gmail.com  +1 650 804 5991 cell