Re: support for large packs and 64-bit offsets

["Shawn O. Pearce" <spearce@spearce.org>]

Nicolas Pitre <nico@cam.org> wrote:
> On Mon, 9 Apr 2007, Shawn O. Pearce wrote:
> 
> > It is unfortunate that we are changing the index file format without
> > also bringing in packv4 support at the same time.  I have just been
> > too swamped in useless bulls**t in day-job work to spend time on
> > Git lately.
> 
> Well... I still did index v2 with pack v4 in mind.  The diference 
> between index v2 and v3 would be minimal.
> 
> Pack v4 is coming along.  Slowly but still coming.

I take it you are working on it alone at this point?  I'd love
to get back into it, but I don't think I've got the cycles for at
least a couple of weeks.


Here's something we didn't think about, but that occurred to me today
when reading this series: If we move the SHA-1 table out of the index
and into the packfile (like we are planning) dumb commit-walkers
(http-fetch) will have problems.  Right now they download the
indexes of every available packfile to determine if they need to
download the corresponding packfile to obtain a needed object.

Moving the SHA-1 table from the index into the packfile will mean
the client cannot do this `optimization'.  Instead it will need to
perform a byte-range request for part of the packfile to decide
if it needs to fetch the remainder of that packfile; or it must
download the entire packfile.  Since not all HTTP servers support
byte-range requests the former may not always be viable and the
latter is obviously not a good idea.

-- 
Shawn.