From: Taylor Blau <me@ttaylorr.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, dstolee@microsoft.com, gitster@pobox.com
Subject: Re: [PATCH v2 1/8] packfile: introduce 'find_kept_pack_entry()'
Date: Tue, 16 Feb 2021 16:48:17 -0500 [thread overview]
Message-ID: <YCw9oX9EEEzo5Kaj@nand.local> (raw)
In-Reply-To: <YCw8TmDdEfcnZSOo@coredump.intra.peff.net>
On Tue, Feb 16, 2021 at 04:42:38PM -0500, Jeff King wrote:
> On Wed, Feb 03, 2021 at 10:58:50PM -0500, Taylor Blau wrote:
>
> > Future callers will want a function to fill a 'struct pack_entry' for a
> > given object id but _only_ from its position in any kept pack(s).
> >
> > In particular, an new 'git repack' mode which ensures the resulting
>
> Nit (not worth re-rolling): s/an new/a new/
Oops. Good eyes.
> > There is a gotcha when looking up objects that are duplicated in kept
> > and non-kept packs, particularly when the MIDX stores the non-kept
> > version and the caller asked for kept objects only. This could be
> > resolved by teaching the MIDX to resolve duplicates by always favoring
> > the kept pack (if one exists), but this breaks an assumption in existing
> > MIDXs, and so it would require a format change.
>
> I don't think this would be possible without a major rethink of how
> midxs work. The "keep" property of a pack is not set in stone when the
> midx is created. You could add a ".keep" file to one of its packs later,
> or even mark one as an in-core keep on the fly. But the duplicate
> resolution happens at creation.
>
> So maybe your "breaks an assumption" is the notion that we do not store
> duplicate information at all in the midx. If so, then I agree. :) But
> I'd also call fixing that more than just a format change.
That's part of it, indeed. The part that I was referring to is that
existing MIDX readers expect duplicates to be resolved in a certain way
(effectively in favor of the pack with the lowest mtime). So the easy
part is indicating a format change which tells new readers how to expect
ties to be broken.
But (as you note) that's only part of the problem: even if we say "ties
are resolved in favor of the lowest mtime pack, or a .keep one, if it
exists", then which ones are kept and which aren't? Even *if* we wrote
that down (which I'm not suggesting we do), kept-ness isn't an immutable
property of the pack, and so I think relying on it is a tricky direction
to take.
> (None of which changes your point, which isn't that it isn't worth
> pursuing that direction).
Yeah; my hope in writing some of this down in the above paragraph is
that it would make clear to future readers that such a MIDX change would
resolve some complexity here, but the complexity it adds in the MIDX
code isn't worth the tradeoff.
> -Peff
Thanks,
Taylor
next prev parent reply other threads:[~2021-02-16 21:49 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 23:23 [PATCH 00/10] repack: support repacking into a geometric sequence Taylor Blau
2021-01-19 23:24 ` [PATCH 01/10] packfile: introduce 'find_kept_pack_entry()' Taylor Blau
2021-01-20 13:40 ` Derrick Stolee
2021-01-20 14:38 ` Taylor Blau
2021-01-29 2:33 ` Junio C Hamano
2021-01-29 18:38 ` Taylor Blau
2021-01-29 19:31 ` Jeff King
2021-01-29 20:20 ` Junio C Hamano
2021-01-19 23:24 ` [PATCH 02/10] revision: learn '--no-kept-objects' Taylor Blau
2021-01-29 3:10 ` Junio C Hamano
2021-01-29 19:13 ` Taylor Blau
2021-01-19 23:24 ` [PATCH 03/10] builtin/pack-objects.c: learn '--assume-kept-packs-closed' Taylor Blau
2021-01-29 3:21 ` Junio C Hamano
2021-01-29 19:19 ` Jeff King
2021-01-29 20:01 ` Taylor Blau
2021-01-29 20:25 ` Jeff King
2021-01-29 22:10 ` Taylor Blau
2021-01-29 22:57 ` Jeff King
2021-01-29 23:03 ` Junio C Hamano
2021-01-29 23:28 ` Taylor Blau
2021-02-02 3:04 ` Taylor Blau
2021-01-29 23:31 ` Jeff King
2021-01-29 22:13 ` Junio C Hamano
2021-01-29 20:30 ` Junio C Hamano
2021-01-29 22:43 ` Jeff King
2021-01-29 22:53 ` Taylor Blau
2021-01-29 23:00 ` Jeff King
2021-01-29 23:10 ` Junio C Hamano
2021-01-19 23:24 ` [PATCH 04/10] p5303: add missing &&-chains Taylor Blau
2021-01-19 23:24 ` [PATCH 05/10] p5303: measure time to repack with keep Taylor Blau
2021-01-29 3:40 ` Junio C Hamano
2021-01-29 19:32 ` Jeff King
2021-01-29 20:04 ` [PATCH] p5303: avoid sed GNU-ism Jeff King
2021-01-29 20:19 ` Eric Sunshine
2021-01-29 20:27 ` Jeff King
2021-01-29 20:36 ` Eric Sunshine
2021-01-29 22:11 ` Taylor Blau
2021-01-29 20:38 ` [PATCH 05/10] p5303: measure time to repack with keep Junio C Hamano
2021-01-29 22:10 ` Jeff King
2021-01-29 23:12 ` Junio C Hamano
2021-01-19 23:24 ` [PATCH 06/10] pack-objects: rewrite honor-pack-keep logic Taylor Blau
2021-01-19 23:24 ` [PATCH 07/10] packfile: add kept-pack cache for find_kept_pack_entry() Taylor Blau
2021-01-19 23:24 ` [PATCH 08/10] builtin/pack-objects.c: teach '--keep-pack-stdin' Taylor Blau
2021-01-19 23:24 ` [PATCH 09/10] builtin/repack.c: extract loose object handling Taylor Blau
2021-01-20 13:59 ` Derrick Stolee
2021-01-20 14:34 ` Taylor Blau
2021-01-20 15:51 ` Derrick Stolee
2021-01-21 3:45 ` Junio C Hamano
2021-01-19 23:24 ` [PATCH 10/10] builtin/repack.c: add '--geometric' option Taylor Blau
2021-01-20 14:05 ` [PATCH 00/10] repack: support repacking into a geometric sequence Derrick Stolee
2021-02-04 3:58 ` [PATCH v2 0/8] " Taylor Blau
2021-02-04 3:58 ` [PATCH v2 1/8] packfile: introduce 'find_kept_pack_entry()' Taylor Blau
2021-02-16 21:42 ` Jeff King
2021-02-16 21:48 ` Taylor Blau [this message]
2021-02-04 3:58 ` [PATCH v2 2/8] revision: learn '--no-kept-objects' Taylor Blau
2021-02-16 23:17 ` Jeff King
2021-02-17 18:35 ` Taylor Blau
2021-02-04 3:59 ` [PATCH v2 3/8] builtin/pack-objects.c: add '--stdin-packs' option Taylor Blau
2021-02-16 23:46 ` Jeff King
2021-02-17 18:59 ` Taylor Blau
2021-02-17 19:21 ` Jeff King
2021-02-04 3:59 ` [PATCH v2 4/8] p5303: add missing &&-chains Taylor Blau
2021-02-04 3:59 ` [PATCH v2 5/8] p5303: measure time to repack with keep Taylor Blau
2021-02-16 23:58 ` Jeff King
2021-02-17 0:02 ` Jeff King
2021-02-17 19:13 ` Taylor Blau
2021-02-17 19:25 ` Jeff King
2021-02-04 3:59 ` [PATCH v2 6/8] builtin/pack-objects.c: rewrite honor-pack-keep logic Taylor Blau
2021-02-17 16:05 ` Jeff King
2021-02-17 19:23 ` Taylor Blau
2021-02-17 19:29 ` Jeff King
2021-02-04 3:59 ` [PATCH v2 7/8] packfile: add kept-pack cache for find_kept_pack_entry() Taylor Blau
2021-02-17 17:11 ` Jeff King
2021-02-17 19:54 ` Taylor Blau
2021-02-17 20:25 ` Jeff King
2021-02-17 20:29 ` Taylor Blau
2021-02-17 21:43 ` Jeff King
2021-02-04 3:59 ` [PATCH v2 8/8] builtin/repack.c: add '--geometric' option Taylor Blau
2021-02-17 18:17 ` Jeff King
2021-02-17 20:01 ` Taylor Blau
2021-02-17 0:01 ` [PATCH v2 0/8] repack: support repacking into a geometric sequence Jeff King
2021-02-17 18:18 ` Jeff King
2021-02-18 3:14 ` [PATCH v3 " Taylor Blau
2021-02-18 3:14 ` [PATCH v3 1/8] packfile: introduce 'find_kept_pack_entry()' Taylor Blau
2021-02-18 3:14 ` [PATCH v3 2/8] revision: learn '--no-kept-objects' Taylor Blau
2021-02-18 3:14 ` [PATCH v3 3/8] builtin/pack-objects.c: add '--stdin-packs' option Taylor Blau
2021-02-18 3:14 ` [PATCH v3 4/8] p5303: add missing &&-chains Taylor Blau
2021-02-18 3:14 ` [PATCH v3 5/8] p5303: measure time to repack with keep Taylor Blau
2021-02-18 3:14 ` [PATCH v3 6/8] builtin/pack-objects.c: rewrite honor-pack-keep logic Taylor Blau
2021-02-18 3:14 ` [PATCH v3 7/8] packfile: add kept-pack cache for find_kept_pack_entry() Taylor Blau
2021-02-18 3:14 ` [PATCH v3 8/8] builtin/repack.c: add '--geometric' option Taylor Blau
2021-02-23 0:31 ` [PATCH v3 0/8] repack: support repacking into a geometric sequence Jeff King
2021-02-23 1:06 ` Taylor Blau
2021-02-23 1:42 ` Jeff King
2021-02-23 2:24 ` [PATCH v4 " Taylor Blau
2021-02-23 2:25 ` [PATCH v4 1/8] packfile: introduce 'find_kept_pack_entry()' Taylor Blau
2021-02-23 2:25 ` [PATCH v4 2/8] revision: learn '--no-kept-objects' Taylor Blau
2021-02-23 2:25 ` [PATCH v4 3/8] builtin/pack-objects.c: add '--stdin-packs' option Taylor Blau
2021-02-23 8:07 ` Junio C Hamano
2021-02-23 18:51 ` Jeff King
2021-02-23 2:25 ` [PATCH v4 4/8] p5303: add missing &&-chains Taylor Blau
2021-02-23 2:25 ` [PATCH v4 5/8] p5303: measure time to repack with keep Taylor Blau
2021-02-23 2:25 ` [PATCH v4 6/8] builtin/pack-objects.c: rewrite honor-pack-keep logic Taylor Blau
2021-02-23 2:25 ` [PATCH v4 7/8] packfile: add kept-pack cache for find_kept_pack_entry() Taylor Blau
2021-02-23 2:25 ` [PATCH v4 8/8] builtin/repack.c: add '--geometric' option Taylor Blau
2021-02-24 23:19 ` Junio C Hamano
2021-02-24 23:43 ` Junio C Hamano
2021-03-04 21:40 ` Taylor Blau
2021-03-04 21:55 ` Taylor Blau
2021-02-23 3:39 ` [PATCH v4 0/8] repack: support repacking into a geometric sequence Jeff King
2021-02-23 7:43 ` Junio C Hamano
2021-02-23 18:44 ` Jeff King
2021-02-23 19:54 ` Martin Fick
2021-02-23 20:06 ` Taylor Blau
2021-02-23 21:57 ` Martin Fick
2021-02-23 20:15 ` Jeff King
2021-02-23 21:41 ` Martin Fick
2021-02-23 21:53 ` Jeff King
2021-02-24 18:13 ` Martin Fick
2021-02-26 6:23 ` Jeff King
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