From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, Duy Nguyen <pclouds@gmail.com>,
"Shawn O. Pearce" <spearce@spearce.org>
Subject: Re: [PATCH 4/6] introduce a commit metapack
Date: Wed, 30 Jan 2013 02:12:09 -0500 [thread overview]
Message-ID: <20130130071209.GD11147@sigill.intra.peff.net> (raw)
In-Reply-To: <7vtxpzq2uv.fsf@alter.siamese.dyndns.org>
On Tue, Jan 29, 2013 at 10:08:08AM -0800, Junio C Hamano wrote:
> > In order to reduce the disk footprint and I/O cost, the future
> > direction for this mechanism may want to point into an existing
> > store of SHA-1 hashes with a shorter file offset, and the .idx file
> > could be such a store, and in order to move in that direction, you
> > cannot avoid tying a metapack to a pack.
>
> Have you considered if we can extend the .idx format version 2
> without actually having to bump the version number? My quick
> reading of check_packed_git_idx() tells me that we have a gap after
> the "large offset table" that we can place extensions, but I may be
> mistaken. If we indeed can, then perhaps adding a series of
>
> 4-byte "id" header
> 4-byte extension length (or 8-byte)
> ... N-byte worth of extension data ...
>
> followed by
>
> 20-byte SHA-1 checksum of all the extension sections
> 8-byte file offset to the first extension section
I considered it, but didn't look into it closely. My feeling was that it
added extra complexity, without adding any real advantage that a
separate file would not.
>From this:
> Then it will be very natural for the extension data that store the
> commit metainfo to name objects in the pack the .idx file describes
> by the offset in the SHA-1 table.
I guess your argument is that putting it all in the same file makes it
more natural for there to be a data dependency.
> As we always say, .idx is a local cache and bumping its version is
> not a huge headache compared to other longer term storage items.
True, but it is even less headache if the file is totally separate and
optional.
-Peff
next prev parent reply other threads:[~2013-01-30 7:12 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-29 9:14 [PATCH/RFC 0/6] commit caching Jeff King
2013-01-29 9:15 ` [PATCH 1/6] csum-file: make sha1write const-correct Jeff King
2013-01-29 9:15 ` [PATCH 2/6] strbuf: add string-chomping functions Jeff King
2013-01-29 10:15 ` Michael Haggerty
2013-01-29 11:10 ` Jeff King
2013-01-30 5:00 ` Michael Haggerty
2013-01-29 9:15 ` [PATCH 3/6] introduce pack metadata cache files Jeff King
2013-01-29 17:35 ` Junio C Hamano
2013-01-30 6:47 ` Jeff King
2013-01-30 1:30 ` Duy Nguyen
2013-01-30 6:50 ` Jeff King
2013-01-29 9:16 ` [PATCH 4/6] introduce a commit metapack Jeff King
2013-01-29 10:24 ` Michael Haggerty
2013-01-29 11:13 ` Jeff King
2013-01-29 17:38 ` Junio C Hamano
2013-01-29 18:08 ` Junio C Hamano
2013-01-30 7:12 ` Jeff King [this message]
2013-01-30 7:17 ` Junio C Hamano
2013-02-01 9:21 ` Jeff King
2013-01-30 15:56 ` Junio C Hamano
2013-01-31 17:03 ` Shawn Pearce
2013-02-01 9:42 ` Jeff King
2013-02-02 17:49 ` Junio C Hamano
2013-01-30 7:07 ` Jeff King
2013-01-30 3:36 ` Duy Nguyen
2013-01-30 7:12 ` Jeff King
2013-01-30 13:56 ` Duy Nguyen
2013-01-30 14:16 ` Duy Nguyen
2013-01-31 11:06 ` Duy Nguyen
2013-02-01 10:15 ` Jeff King
2013-02-02 9:49 ` Duy Nguyen
2013-02-01 10:40 ` Jeff King
2013-03-17 13:21 ` Duy Nguyen
2013-03-18 12:20 ` Jeff King
2013-02-01 10:00 ` Jeff King
2013-01-29 9:16 ` [PATCH 5/6] add git-metapack command Jeff King
2013-01-29 9:16 ` [PATCH 6/6] commit: look up commit info in metapack Jeff King
2013-01-30 3:31 ` [PATCH/RFC 0/6] commit caching Duy Nguyen
2013-01-30 7:18 ` Jeff King
2013-01-30 8:32 ` Duy Nguyen
2013-01-31 17:14 ` Shawn Pearce
2013-02-01 9:11 ` Jeff King
2013-02-02 10:04 ` Shawn Pearce
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