Subject: Re: [PATCH] RFC: git lazy clone proof-of-concept

From: "Shawn O. Pearce" <[email-masked]>
Date: Sun, 17 Feb 2008 03:18:41 -0500

Nicolas Pitre <[email-masked]> wrote:
> 
> I should really come around to fixing packed_object_info_detail() for 
> the OBJ_OFS_DELTA case one day.

Please don't.

Obtaining the SHA-1 of your delta base would require unpacking your
delta base and then doing a SHA-1 hash of it.  Or alternatively
doing a search through the .idx for the object that starts at the
requested OFS.  Either way, its really expensive for a minor detail
of output in verify-pack.  Something that any script can produce
with a simple reverse lookup table.

Its also run after we just spent a hell of a lot of time and disk
IO trying to verify the packfile.  We slammed through the pack
once to do its overall SHA-1, and then god knows how many times as
we iterate the objects in pack order, not delta base order, thus
causing the delta base cache to become overwhelmed and constantly
fault out entries.  Pack verification is stupid and slow.  This
would make -v even worse.

But if you are going to do that, you may also want to fix the
"*store_size = 0 /* notyet */" that's like 5 lines above.  :)

BTW, why does this return const char* from typename(type) instead
of just returning the enum object_type and letting the caller do
typename() if they want it?  Most of our other code that returns
types returns the enum, not the string.  :-\

-- 
Shawn.