92fa3253c8
When iterating towards the next record in a reftable block we need to
keep track of the key that the last record had. This is required because
reftable records use prefix compression, where subsequent records may
reuse parts of their preceding record's key.
This key is stored in the `block_iter::last_key`, which we update after
every call to `block_iter_next()`: we simply reset the buffer and then
add the current key to it.
This is a bit inefficient though because it requires us to copy over the
key on every iteration, which adds up when iterating over many records.
Instead, we can make use of the fact that the `block_iter::key` buffer
is basically only a scratch buffer. So instead of copying over contents,
we can just swap both buffers.
The following benchmark prints a single ref matching a specific pattern
out of 1 million refs via git-show-ref(1):
Benchmark 1: show-ref: single matching ref (revision = HEAD~)
Time (mean ± σ): 155.7 ms ± 5.0 ms [User: 152.1 ms, System: 3.4 ms]
Range (min … max): 150.8 ms … 185.7 ms 1000 runs
Benchmark 2: show-ref: single matching ref (revision = HEAD)
Time (mean ± σ): 150.8 ms ± 4.2 ms [User: 147.1 ms, System: 3.5 ms]
Range (min … max): 145.1 ms … 180.7 ms 1000 runs
Summary
show-ref: single matching ref (revision = HEAD) ran
1.03 ± 0.04 times faster than show-ref: single matching ref (revision = HEAD~)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-<commandname>.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.txt
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission and Documentation/CodingGuidelines).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
To subscribe to the list, send an email to git+subscribe@vger.kernel.org (see https://subspace.kernel.org/subscribing.html for details). The mailing list archives are available at https://lore.kernel.org/git/, https://marc.info/?l=git and other archival sites.
Issues which are security relevant should be disclosed privately to the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks