From: Taylor Blau <me@ttaylorr.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, dstolee@microsoft.com, gitster@pobox.com,
jrnieder@gmail.com
Subject: Re: [PATCH v2 2/8] pack-write.c: prepare to write 'pack-*.rev' files
Date: Mon, 25 Jan 2021 14:15:18 -0500 [thread overview]
Message-ID: <YA8YxtUUwE0lLxQt@nand.local> (raw)
In-Reply-To: <YAtey9krU32mgEBV@coredump.intra.peff.net>
On Fri, Jan 22, 2021 at 06:24:59PM -0500, Jeff King wrote:
> On Wed, Jan 13, 2021 at 05:28:11PM -0500, Taylor Blau wrote:
>
> [...]
>
> qsort? Don't we have a perfectly good radix sort for this exact purpose? :)
Yeah, I think your argument against it (which I agree with is
basically):
We could, and it would be faster, but it would (1) require allocating
twice as much data, and (2) the speed increase is a drop in the bucket
on any repository with enough objects to even notice it.
I'll add something to that effect to the commit message.
> Dereferencing a pointer to index another array always makes me nervous
> that we may have a bounds problem with bogus data.
>
> In this case we know it is OK because we filled the array ourselves with
> in-bound numbers in write_rev_index_positions.
Right.
> I was surprised we didn't define these already on the reading side, but
> it looks like we didn't. In patch 1, we probably should be checking
> RIDX_SIGNATURE in load_revindex_from_disk(). But much more importantly,
> we should be checking that we find version 1, since that's what will
> make it safe to later invent a version 2.
:-). Thanks for noticing, fixed.
> I forgot to comment on this in patch 1, but: I think the format is
> really independent of the hash size. The contents are identical for a
> sha-1 versus sha-256 file.
Right; the format is identical. That is, the fields are the same, but
the hashes are longer.
> That said, I don't overly mind having a hash identifier if it might help
> debug things (OTOH, how the heck do you end up with one that matches the
> trailer's packfile but _doesn't_ match the trailer's contents?).
>
> If we do have it, should we also be checking it in the loading function?
I'm not opposed to it, but I imagined that this field would be primarily
for debugging purposes. I was surprised to learn that we _don't_ verify
the checksum for .idx files. So, I'm reluctant to start doing so here,
honestly.
> So if the caller gave us a name, we force-overwrite it. That seemed
> weird to me at first, but it makes sense; the atomic rename-into-place
> writers will not be passing in the name. And this is exactly how
> write_idx_file() works.
Yep.
> I wonder if we could factor out some of this repeated logic, but I
> suspect it is mostly diminishing returns. Maybe this "open a pack file
> for writing" could become a helper function, though.
Yeah. I tried factoring it out before replying, and it's a little gross.
Most of my discomfort with it lies in the complexity of the parameters.
Consider extracting the code in write_idx_file():
- There would need to be a double pointer for 'index_name' (which is
sometimes read, and sometimes written to).
- There would be an unsigned bit for "verify" (i.e., "open with
hashfd_check() or not").
- There would be a "pattern" variable if we were creating a new
temporary file with odb_mkstemp().
Having the caller be forced to juggle the combinations of passing
NULL/0 or not for each of those three makes me leery that this is worth
doing, so I tend to agree with your judgement that this provides a
diminishing return.
Thanks,
Taylor
next prev parent reply other threads:[~2021-01-26 21:06 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-08 18:19 [PATCH 0/8] pack-revindex: introduce on-disk '.rev' format Taylor Blau
2021-01-08 18:19 ` [PATCH 1/8] packfile: prepare for the existence of '*.rev' files Taylor Blau
2021-01-08 18:20 ` [PATCH 2/8] pack-write.c: prepare to write 'pack-*.rev' files Taylor Blau
2021-01-08 18:20 ` [PATCH 3/8] builtin/index-pack.c: write reverse indexes Taylor Blau
2021-01-08 18:20 ` [PATCH 4/8] builtin/pack-objects.c: respect 'pack.writeReverseIndex' Taylor Blau
2021-01-08 18:20 ` [PATCH 5/8] Documentation/config/pack.txt: advertise 'pack.writeReverseIndex' Taylor Blau
2021-01-08 18:20 ` [PATCH 6/8] t: prepare for GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-12 17:11 ` Ævar Arnfjörð Bjarmason
2021-01-12 18:40 ` Taylor Blau
2021-01-08 18:20 ` [PATCH 7/8] t: support GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-12 16:49 ` Derrick Stolee
2021-01-12 17:34 ` Taylor Blau
2021-01-12 17:18 ` Ævar Arnfjörð Bjarmason
2021-01-12 17:39 ` Derrick Stolee
2021-01-12 18:17 ` Taylor Blau
2021-01-08 18:20 ` [PATCH 8/8] pack-revindex: ensure that on-disk reverse indexes are given precedence Taylor Blau
2021-01-13 22:28 ` [PATCH v2 0/8] pack-revindex: introduce on-disk '.rev' format Taylor Blau
2021-01-13 22:28 ` [PATCH v2 1/8] packfile: prepare for the existence of '*.rev' files Taylor Blau
2021-01-14 7:22 ` Junio C Hamano
2021-01-14 12:07 ` Derrick Stolee
2021-01-14 19:57 ` Jeff King
2021-01-14 18:28 ` Taylor Blau
2021-01-14 7:26 ` Junio C Hamano
2021-01-14 18:13 ` Taylor Blau
2021-01-14 20:57 ` Junio C Hamano
2021-01-22 22:54 ` Jeff King
2021-01-25 17:44 ` Taylor Blau
2021-01-25 18:27 ` Jeff King
2021-01-25 19:04 ` Junio C Hamano
2021-01-25 19:23 ` Taylor Blau
2021-01-13 22:28 ` [PATCH v2 2/8] pack-write.c: prepare to write 'pack-*.rev' files Taylor Blau
2021-01-22 23:24 ` Jeff King
2021-01-25 19:15 ` Taylor Blau [this message]
2021-01-26 21:43 ` Jeff King
2021-01-13 22:28 ` [PATCH v2 3/8] builtin/index-pack.c: write reverse indexes Taylor Blau
2021-01-22 23:53 ` Jeff King
2021-01-25 20:03 ` Taylor Blau
2021-01-13 22:28 ` [PATCH v2 4/8] builtin/pack-objects.c: respect 'pack.writeReverseIndex' Taylor Blau
2021-01-22 23:57 ` Jeff King
2021-01-23 0:08 ` Jeff King
2021-01-25 20:21 ` Taylor Blau
2021-01-25 20:50 ` Jeff King
2021-01-13 22:28 ` [PATCH v2 5/8] Documentation/config/pack.txt: advertise 'pack.writeReverseIndex' Taylor Blau
2021-01-13 22:28 ` [PATCH v2 6/8] t: prepare for GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-13 22:28 ` [PATCH v2 7/8] t: support GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-13 22:28 ` [PATCH v2 8/8] pack-revindex: ensure that on-disk reverse indexes are given precedence Taylor Blau
2021-01-25 23:37 ` [PATCH v3 00/10] pack-revindex: introduce on-disk '.rev' format Taylor Blau
2021-01-25 23:37 ` [PATCH v3 01/10] packfile: prepare for the existence of '*.rev' files Taylor Blau
2021-01-29 0:27 ` Jeff King
2021-01-29 1:14 ` Taylor Blau
2021-01-30 8:39 ` Jeff King
2021-01-25 23:37 ` [PATCH v3 02/10] pack-write.c: prepare to write 'pack-*.rev' files Taylor Blau
2021-01-25 23:37 ` [PATCH v3 03/10] builtin/index-pack.c: allow stripping arbitrary extensions Taylor Blau
2021-01-29 0:28 ` Jeff King
2021-01-29 1:15 ` Taylor Blau
2021-01-25 23:37 ` [PATCH v3 04/10] builtin/index-pack.c: write reverse indexes Taylor Blau
2021-01-25 23:37 ` [PATCH v3 05/10] builtin/pack-objects.c: respect 'pack.writeReverseIndex' Taylor Blau
2021-01-25 23:37 ` [PATCH v3 06/10] Documentation/config/pack.txt: advertise 'pack.writeReverseIndex' Taylor Blau
2021-01-29 0:30 ` Jeff King
2021-01-29 1:17 ` Taylor Blau
2021-01-30 8:41 ` Jeff King
2021-01-25 23:37 ` [PATCH v3 07/10] t: prepare for GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-29 0:45 ` Jeff King
2021-01-29 1:09 ` Eric Sunshine
2021-01-29 1:21 ` Taylor Blau
2021-01-30 8:43 ` Jeff King
2021-01-29 2:42 ` Junio C Hamano
2021-01-25 23:37 ` [PATCH v3 08/10] t: support GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-29 0:47 ` Jeff King
2021-01-25 23:37 ` [PATCH v3 09/10] pack-revindex: ensure that on-disk reverse indexes are given precedence Taylor Blau
2021-01-29 0:53 ` Jeff King
2021-01-29 1:25 ` Taylor Blau
2021-01-30 8:46 ` Jeff King
2021-01-25 23:37 ` [PATCH v3 10/10] t5325: check both on-disk and in-memory reverse index Taylor Blau
2021-01-29 1:04 ` Jeff King
2021-01-29 1:05 ` Jeff King
2021-01-29 1:32 ` Taylor Blau
2021-01-30 8:47 ` Jeff King
2021-01-26 2:36 ` [PATCH v3 00/10] pack-revindex: introduce on-disk '.rev' format Junio C Hamano
2021-01-26 2:49 ` Taylor Blau
2021-01-29 1:06 ` Jeff King
2021-01-29 1:34 ` Taylor Blau
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