From: Duy Nguyen <pclouds@gmail.com>
To: Derrick Stolee <stolee@gmail.com>
Cc: "Jeff Hostetler" <git@jeffhostetler.com>,
"Git Mailing List" <git@vger.kernel.org>,
"Junio C Hamano" <gitster@pobox.com>, "Jeff King" <peff@peff.net>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
"Johannes Schindelin" <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH v2 05/10] split-index.c: dump "link" extension as json
Date: Thu, 27 Jun 2019 20:47:54 +0700 [thread overview]
Message-ID: <CACsJy8BeUOv+He5c58iGO47XDkoKkAGQZqH0NM1fZcb2ESFscQ@mail.gmail.com> (raw)
In-Reply-To: <f4f82ab4-2846-34f9-45ee-a2149fb15d17@gmail.com>
On Thu, Jun 27, 2019 at 8:42 PM Derrick Stolee <stolee@gmail.com> wrote:
>
> On 6/27/2019 9:24 AM, Jeff Hostetler wrote:
> > On 6/27/2019 6:48 AM, Duy Nguyen wrote:
> >> On Tue, Jun 25, 2019 at 7:40 PM Derrick Stolee <stolee@gmail.com> wrote:
> >>>
> >>> On 6/25/2019 6:29 AM, Duy Nguyen wrote:
> >>>> On Tue, Jun 25, 2019 at 3:06 AM Jeff Hostetler <git@jeffhostetler.com> wrote:
> >>>>> I'm curious how big these EWAHs will be in practice and
> >>>>> how useful an array of integers will be (especially as the
> >>>>> pretty format will be one integer per line). Perhaps it
> >>>>> would helpful to have an extended example in one of the
> >>>>> tests.
> >>>>
> >>>> It's one integer per updated entry. So if you have a giant index and
> >>>> updated every single one of them, the EWAH bitmap contains that many
> >>>> integers.
> >>>>
> >>>> If it was easy to just merge these bitmaps back to the entry (e.g. in
> >>>> this example, add "replaced": true to entry zero) I would have done
> >>>> it. But we dump as we stream and it's already too late to do it.
> >>>>
> >>>>> Would it be better to have the caller of ewah_each_bit()
> >>>>> build a hex or bit string in a strbuf and then write it
> >>>>> as a single string?
> >>>>
> >>>> I don't think the current EWAH representation is easy to read in the
> >>>> first place. You'll probably have to run through some script to update
> >>>> the main entries part and will have a much better view, but that's
> >>>> pretty quick. If it's for scripts, then it's probably best to keep as
> >>>> an array of integers, not a string. Less post processing.
> >>>
> >>> I don't think the intent is to dump the EWAH directly, but instead to
> >>> dump a string of the uncompressed bitmap. Something like:
> >>>
> >>> "delete_bitmap" : "01101101101"
> >>>
> >>> instead of
> >>>
> >>> "delete_bitmap" : [ 0, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1 ]
> >>
> >> I get this part. But the numbers in the array were the position of the
> >> set bits. It's not showing just the actual bit map.
> >>
> >> The same bitmap would be currently displayed as
> >>
> >> "delete_bitmap": [ 1, 2, 4, 5, 7, 8, 9, 11 ]
> >>
> >> And that maps back to the entry[1], entry[2], entry[4]... in the index
> >> being deleted from the base index. So displaying as a real bit map
> >> actually adds more work for both the reader and the tool because you
> >> have to calculate the position either way. And it gets harder if the
> >> bit you're intereted in is on the far right.
> >
> >
> > Thanks for the clarification. That helps.
>
> Same here! We expect these to be much smaller than the full set, correct?
For split-index, the number of 1 bits should be about the size of your
working set, not the index size. In the normal case, then yes it
should be much smaller. After a big merge or branch switch, it could
get as big as the index. But I would hope the logic to re-split the
index kicks in, which essentially empties these bitmaps.
EWAH bitmap is also used in UNTR extension if I remember correctly.
Those bitmaps may have as many bits as the directories you have in the
index.
> Thanks,
> -Stolee
>
--
Duy
next prev parent reply other threads:[~2019-06-27 13:48 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-24 13:02 [PATCH v2 00/10] Add 'ls-files --debug-json' to dump the index in json Nguyễn Thái Ngọc Duy
2019-06-24 13:02 ` [PATCH v2 01/10] ls-files: add --json to dump the index Nguyễn Thái Ngọc Duy
2019-06-24 19:15 ` Jeff Hostetler
2019-06-24 20:04 ` Junio C Hamano
2019-06-25 9:21 ` Johannes Schindelin
2019-06-25 9:52 ` Duy Nguyen
2019-06-25 15:37 ` Jeff Hostetler
2019-06-25 9:05 ` Thomas Gummerer
2019-06-25 9:44 ` Johannes Schindelin
2019-06-25 11:31 ` Johannes Schindelin
2019-06-25 13:57 ` Johannes Schindelin
2019-06-25 22:28 ` Junio C Hamano
2019-06-26 19:51 ` Junio C Hamano
2019-06-24 13:02 ` [PATCH v2 02/10] read-cache.c: dump common extension info in json Nguyễn Thái Ngọc Duy
2019-06-24 13:02 ` [PATCH v2 03/10] cache-tree.c: dump "TREE" extension as json Nguyễn Thái Ngọc Duy
2019-06-24 13:02 ` [PATCH v2 04/10] dir.c: dump "UNTR" " Nguyễn Thái Ngọc Duy
2019-06-24 19:32 ` Jeff Hostetler
2019-06-24 13:02 ` [PATCH v2 05/10] split-index.c: dump "link" " Nguyễn Thái Ngọc Duy
2019-06-24 20:06 ` Jeff Hostetler
2019-06-25 10:29 ` Duy Nguyen
2019-06-25 12:40 ` Derrick Stolee
2019-06-27 10:48 ` Duy Nguyen
2019-06-27 13:24 ` Jeff Hostetler
2019-06-27 13:42 ` Derrick Stolee
2019-06-27 13:47 ` Duy Nguyen [this message]
2019-07-03 9:08 ` SZEDER Gábor
2019-07-04 20:01 ` SZEDER Gábor
2019-07-04 23:54 ` Duy Nguyen
2019-07-08 17:58 ` Junio C Hamano
2019-06-24 13:02 ` [PATCH v2 06/10] fsmonitor.c: dump "FSMN" " Nguyễn Thái Ngọc Duy
2019-06-24 13:02 ` [PATCH v2 07/10] resolve-undo.c: dump "REUC" " Nguyễn Thái Ngọc Duy
2019-06-24 13:02 ` [PATCH v2 08/10] read-cache.c: dump "EOIE" " Nguyễn Thái Ngọc Duy
2019-06-24 13:02 ` [PATCH v2 09/10] read-cache.c: dump "IEOT" " Nguyễn Thái Ngọc Duy
2019-06-24 13:02 ` [PATCH v2 10/10] t3008: use the new SINGLE_CPU prereq Nguyễn Thái Ngọc Duy
2019-06-24 18:00 ` [PATCH v2 00/10] Add 'ls-files --debug-json' to dump the index in json Johannes Schindelin
2019-06-24 18:39 ` Jeff Hostetler
2019-06-25 9:05 ` Duy Nguyen
2019-06-25 9:38 ` Thomas Gummerer
2019-06-25 11:27 ` Johannes Schindelin
2019-06-25 12:06 ` Duy Nguyen
2019-06-25 14:10 ` Johannes Schindelin
2019-06-25 17:08 ` Ramsay Jones
2019-06-26 15:05 ` Johannes Schindelin
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