From: Derrick Stolee <stolee@gmail.com>
To: Taylor Blau <me@ttaylorr.com>, git@vger.kernel.org
Cc: dstolee@microsoft.com, gitster@pobox.com, peff@peff.net
Subject: Re: [PATCH 7/9] pack-revindex: read multi-pack reverse indexes
Date: Wed, 10 Feb 2021 21:53:23 -0500 [thread overview]
Message-ID: <3680ce51-81ba-d6a3-a0b6-6f3a7cc14503@gmail.com> (raw)
In-Reply-To: <4c5e64c5fcb2948a0598d6e0c70097a9561716a9.1612998106.git.me@ttaylorr.com>
On 2/10/21 6:03 PM, Taylor Blau wrote:
> Implement reading for multi-pack reverse indexes, as described in the
> previous patch.
>
> Note that these functions don't yet have any callers, and won't until
> multi-pack reachability bitmaps are introduced in a later patch series.
> In the meantime, this patch implements some of the infrastructure
> necessary to support multi-pack bitmaps.
>
> There are three new functions exposed by the revindex API:
>
> - load_midx_revindex(): loads the reverse index corresponding to the
> given multi-pack index.
>
> - midx_to_pack_pos() and pack_pos_to_midx(): these convert between the
> multi-pack index and pseudo-pack order.
>
> load_midx_revindex() and pack_pos_to_midx() are both relatively
> straightforward.
>
> load_midx_revindex() needs a few functions to be exposed from the midx
> API. One to get the checksum of a midx, and another to get the .rev's
> filename. Similar to recent changes in the packed_git struct, three new
> fields are added to the multi_pack_index struct: one to keep track of
> the size, one to keep track of the mmap'd pointer, and another to point
> past the header and at the reverse index's data.
>
> pack_pos_to_midx() simply reads the corresponding entry out of the
> table.
>
> midx_to_pack_pos() is the trickiest, since it needs to find an object's
> position in the psuedo-pack order, but that order can only be recovered
> in the .rev file itself. This mapping can be implemented with a binary
> search, but note that the thing we're binary searching over isn't an
> array, but rather a _permutation_.
>
> So, when comparing two items, it's helpful to keep in mind the
> difference. Instead of a traditional binary search, where you are
> comparing two things directly, here we're comparing a (pack, offset)
> tuple with an index into the multi-pack index. That index describes
> another (pack, offset) tuple, and it is _those_ two tuples that are
> compared.
>
> Signed-off-by: Taylor Blau <me@ttaylorr.com>
> ---
> midx.c | 11 +++++
> midx.h | 6 +++
> pack-revindex.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++
> pack-revindex.h | 46 ++++++++++++++++++++
> packfile.c | 3 ++
> 5 files changed, 178 insertions(+)
>
> diff --git a/midx.c b/midx.c
> index bf258c4fde..12bfce8bb1 100644
> --- a/midx.c
> +++ b/midx.c
> @@ -48,11 +48,22 @@ static uint8_t oid_version(void)
> }
> }
>
> +static const unsigned char *get_midx_checksum(struct multi_pack_index *m)
> +{
> + return m->data + m->data_len - the_hash_algo->rawsz;
'struct multi_pack_index' has a 'hash_len' member that you could
use here. It would allow a different hash length in the stored
file than the one required by the repository. Except...
> +}
> +
> static char *get_midx_filename(const char *object_dir)
> {
> return xstrfmt("%s/pack/multi-pack-index", object_dir);
> }
>
> +char *get_midx_rev_filename(struct multi_pack_index *m)
> +{
> + return xstrfmt("%s/pack/multi-pack-index-%s.rev",
> + m->object_dir, hash_to_hex(get_midx_checksum(m)));
...this assumes the hash is of the same length as the_hash_algo,
so you are doing the right thing. Currently, I think we check
that 'm->hash_len == the_hash_algo->rawsz' on load. We'll need
to check this again later when in the transition phase of the
new hash work.
(No changes are needed to your patch.)
Thanks,
-Stolee
next prev parent reply other threads:[~2021-02-11 2:55 UTC|newest]
Thread overview: 171+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-10 23:02 [PATCH 0/9] midx: implement a multi-pack reverse index Taylor Blau
2021-02-10 23:02 ` [PATCH 1/9] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-02-11 2:27 ` Derrick Stolee
2021-02-11 2:34 ` Taylor Blau
2021-02-10 23:02 ` [PATCH 2/9] midx: allow marking a pack as preferred Taylor Blau
2021-02-11 19:33 ` SZEDER Gábor
2021-02-15 15:49 ` Taylor Blau
2021-02-15 17:01 ` Ævar Arnfjörð Bjarmason
2021-02-15 18:41 ` [PATCH 0/5] commit-graph: parse_options() cleanup Ævar Arnfjörð Bjarmason
2021-02-15 18:41 ` [PATCH 1/5] commit-graph: define common usage with a macro Ævar Arnfjörð Bjarmason
2021-02-16 11:33 ` Derrick Stolee
2021-02-15 18:41 ` [PATCH 2/5] commit-graph: remove redundant handling of -h Ævar Arnfjörð Bjarmason
2021-02-16 11:35 ` Derrick Stolee
2021-02-15 18:41 ` [PATCH 3/5] commit-graph: use parse_options_concat() Ævar Arnfjörð Bjarmason
2021-02-15 18:51 ` Taylor Blau
2021-02-15 19:53 ` Taylor Blau
2021-02-15 20:39 ` Ævar Arnfjörð Bjarmason
2021-09-17 21:13 ` SZEDER Gábor
2021-09-17 22:03 ` Jeff King
2021-09-18 4:30 ` Taylor Blau
2021-09-18 7:20 ` Ævar Arnfjörð Bjarmason
2021-09-18 15:56 ` Taylor Blau
2021-09-18 15:58 ` Taylor Blau
2021-09-18 0:58 ` Ævar Arnfjörð Bjarmason
2021-02-15 18:41 ` [PATCH 4/5] commit-graph: refactor dispatch loop for style Ævar Arnfjörð Bjarmason
2021-02-15 18:53 ` Taylor Blau
2021-02-16 11:40 ` Derrick Stolee
2021-02-16 12:02 ` Ævar Arnfjörð Bjarmason
2021-02-16 18:28 ` Derrick Stolee
2021-02-15 18:41 ` [PATCH 5/5] commit-graph: show usage on "commit-graph [write|verify] garbage" Ævar Arnfjörð Bjarmason
2021-02-15 19:06 ` Taylor Blau
2021-02-16 11:43 ` Derrick Stolee
2021-02-15 21:01 ` [PATCH v2 0/4] midx: split out sub-commands Taylor Blau
2021-02-15 21:01 ` [PATCH v2 1/4] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-02-15 21:01 ` [PATCH v2 2/4] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-02-15 21:39 ` Ævar Arnfjörð Bjarmason
2021-02-15 21:45 ` Taylor Blau
2021-02-16 11:47 ` Derrick Stolee
2021-02-15 21:01 ` [PATCH v2 3/4] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-02-15 21:01 ` [PATCH v2 4/4] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-02-15 21:54 ` Ævar Arnfjörð Bjarmason
2021-02-15 22:34 ` Taylor Blau
2021-02-15 23:11 ` Ævar Arnfjörð Bjarmason
2021-02-15 23:49 ` Taylor Blau
2021-02-16 11:50 ` [PATCH v2 0/4] midx: split out sub-commands Derrick Stolee
2021-02-16 14:28 ` Taylor Blau
2021-02-10 23:02 ` [PATCH 3/9] midx: don't free midx_name early Taylor Blau
2021-02-10 23:02 ` [PATCH 4/9] midx: keep track of the checksum Taylor Blau
2021-02-11 2:33 ` Derrick Stolee
2021-02-11 2:35 ` Taylor Blau
2021-02-10 23:03 ` [PATCH 5/9] midx: make some functions non-static Taylor Blau
2021-02-10 23:03 ` [PATCH 6/9] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-02-11 2:48 ` Derrick Stolee
2021-02-11 3:03 ` Taylor Blau
2021-02-10 23:03 ` [PATCH 7/9] pack-revindex: read " Taylor Blau
2021-02-11 2:53 ` Derrick Stolee [this message]
2021-02-11 3:04 ` Taylor Blau
2021-02-11 7:54 ` Junio C Hamano
2021-02-11 14:54 ` Taylor Blau
2021-02-10 23:03 ` [PATCH 8/9] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-02-10 23:03 ` [PATCH 9/9] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-02-11 2:58 ` [PATCH 0/9] midx: implement a multi-pack reverse index Derrick Stolee
2021-02-11 3:06 ` Taylor Blau
2021-02-11 8:13 ` Junio C Hamano
2021-02-11 18:37 ` Derrick Stolee
2021-02-11 18:55 ` Junio C Hamano
2021-02-24 19:09 ` [PATCH v2 00/15] " Taylor Blau
2021-02-24 19:09 ` [PATCH v2 01/15] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-02-24 19:09 ` [PATCH v2 02/15] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-02-24 19:09 ` [PATCH v2 03/15] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-02-24 19:09 ` [PATCH v2 04/15] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-03-02 4:06 ` Jonathan Tan
2021-03-02 19:02 ` Taylor Blau
2021-03-04 1:54 ` Jonathan Tan
2021-03-04 3:02 ` Taylor Blau
2021-02-24 19:09 ` [PATCH v2 05/15] builtin/multi-pack-index.c: don't enter bogus cmd_mode Taylor Blau
2021-02-24 19:09 ` [PATCH v2 06/15] builtin/multi-pack-index.c: display usage on unrecognized command Taylor Blau
2021-02-24 19:09 ` [PATCH v2 07/15] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-02-24 19:09 ` [PATCH v2 08/15] midx: allow marking a pack as preferred Taylor Blau
2021-03-02 4:17 ` Jonathan Tan
2021-03-02 19:09 ` Taylor Blau
2021-03-04 2:00 ` Jonathan Tan
2021-03-04 3:04 ` Taylor Blau
2021-02-24 19:09 ` [PATCH v2 09/15] midx: don't free midx_name early Taylor Blau
2021-02-24 19:10 ` [PATCH v2 10/15] midx: keep track of the checksum Taylor Blau
2021-02-24 19:10 ` [PATCH v2 11/15] midx: make some functions non-static Taylor Blau
2021-02-24 19:10 ` [PATCH v2 12/15] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-03-02 4:21 ` Jonathan Tan
2021-03-02 4:36 ` Taylor Blau
2021-03-02 19:15 ` Taylor Blau
2021-03-04 2:03 ` Jonathan Tan
2021-02-24 19:10 ` [PATCH v2 13/15] pack-revindex: read " Taylor Blau
2021-03-02 18:36 ` Jonathan Tan
2021-03-03 15:27 ` Taylor Blau
2021-02-24 19:10 ` [PATCH v2 14/15] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-02-24 19:10 ` [PATCH v2 15/15] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-03-02 18:40 ` Jonathan Tan
2021-03-03 15:30 ` Taylor Blau
2021-03-04 2:04 ` Jonathan Tan
2021-03-04 3:06 ` Taylor Blau
2021-03-11 17:04 ` [PATCH v3 00/16] midx: implement a multi-pack reverse index Taylor Blau
2021-03-11 17:04 ` [PATCH v3 01/16] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-03-29 11:20 ` Jeff King
2021-03-11 17:04 ` [PATCH v3 02/16] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-03-29 11:22 ` Jeff King
2021-03-11 17:04 ` [PATCH v3 03/16] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-03-11 17:04 ` [PATCH v3 04/16] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-03-29 11:36 ` Jeff King
2021-03-29 20:38 ` Taylor Blau
2021-03-30 7:04 ` Jeff King
2021-03-11 17:04 ` [PATCH v3 05/16] builtin/multi-pack-index.c: don't enter bogus cmd_mode Taylor Blau
2021-03-11 17:04 ` [PATCH v3 06/16] builtin/multi-pack-index.c: display usage on unrecognized command Taylor Blau
2021-03-29 11:42 ` Jeff King
2021-03-29 20:41 ` Taylor Blau
2021-03-11 17:05 ` [PATCH v3 07/16] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-03-11 17:05 ` [PATCH v3 08/16] midx: allow marking a pack as preferred Taylor Blau
2021-03-29 12:00 ` Jeff King
2021-03-29 21:15 ` Taylor Blau
2021-03-30 7:11 ` Jeff King
2021-03-11 17:05 ` [PATCH v3 09/16] midx: don't free midx_name early Taylor Blau
2021-03-11 17:05 ` [PATCH v3 10/16] midx: keep track of the checksum Taylor Blau
2021-03-11 17:05 ` [PATCH v3 11/16] midx: make some functions non-static Taylor Blau
2021-03-11 17:05 ` [PATCH v3 12/16] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-03-29 12:12 ` Jeff King
2021-03-29 21:22 ` Taylor Blau
2021-03-11 17:05 ` [PATCH v3 13/16] pack-revindex: read " Taylor Blau
2021-03-29 12:43 ` Jeff King
2021-03-29 21:27 ` Taylor Blau
2021-03-11 17:05 ` [PATCH v3 14/16] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-03-11 17:05 ` [PATCH v3 15/16] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-03-29 12:53 ` Jeff King
2021-03-29 21:30 ` Taylor Blau
2021-03-11 17:05 ` [PATCH v3 16/16] midx.c: improve cache locality in midx_pack_order_cmp() Taylor Blau
2021-03-29 12:59 ` Jeff King
2021-03-29 21:34 ` Taylor Blau
2021-03-30 7:15 ` Jeff King
2021-03-12 15:16 ` [PATCH v3 00/16] midx: implement a multi-pack reverse index Derrick Stolee
2021-03-29 13:05 ` Jeff King
2021-03-29 21:30 ` Junio C Hamano
2021-03-29 21:37 ` Taylor Blau
2021-03-30 7:15 ` Jeff King
2021-03-30 13:37 ` Taylor Blau
2021-03-30 15:03 ` [PATCH v4 " Taylor Blau
2021-03-30 15:03 ` [PATCH v4 01/16] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-03-30 15:03 ` [PATCH v4 02/16] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-03-30 15:03 ` [PATCH v4 03/16] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-03-30 15:03 ` [PATCH v4 04/16] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-03-30 15:04 ` [PATCH v4 05/16] builtin/multi-pack-index.c: don't enter bogus cmd_mode Taylor Blau
2021-03-30 15:04 ` [PATCH v4 06/16] builtin/multi-pack-index.c: display usage on unrecognized command Taylor Blau
2021-03-30 15:04 ` [PATCH v4 07/16] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-03-30 15:04 ` [PATCH v4 08/16] midx: allow marking a pack as preferred Taylor Blau
2021-04-01 0:32 ` Taylor Blau
2021-03-30 15:04 ` [PATCH v4 09/16] midx: don't free midx_name early Taylor Blau
2021-03-30 15:04 ` [PATCH v4 10/16] midx: keep track of the checksum Taylor Blau
2021-03-30 15:04 ` [PATCH v4 11/16] midx: make some functions non-static Taylor Blau
2021-03-30 15:04 ` [PATCH v4 12/16] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-03-30 15:04 ` [PATCH v4 13/16] pack-revindex: read " Taylor Blau
2021-03-30 15:04 ` [PATCH v4 14/16] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-09-08 1:08 ` [PATCH] pack-write: skip *.rev work when not writing *.rev Ævar Arnfjörð Bjarmason
2021-09-08 1:35 ` Carlo Arenas
2021-09-08 2:42 ` Taylor Blau
2021-09-08 15:47 ` Junio C Hamano
2021-09-08 2:50 ` Taylor Blau
2021-09-08 3:50 ` Taylor Blau
2021-09-08 10:18 ` Ævar Arnfjörð Bjarmason
2021-09-08 16:32 ` Taylor Blau
2021-03-30 15:04 ` [PATCH v4 15/16] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-03-30 15:04 ` [PATCH v4 16/16] midx.c: improve cache locality in midx_pack_order_cmp() Taylor Blau
2021-03-30 15:45 ` [PATCH v4 00/16] midx: implement a multi-pack reverse index Jeff King
2021-03-30 15:49 ` Taylor Blau
2021-03-30 16:01 ` Jeff King
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