commit | 31e3cb4375f92e56f27b83c4583523c14a712b2d | [log] [tgz] |
---|---|---|
author | Gal Paikin <paiking@google.com> | Mon Dec 07 15:18:34 2020 +0100 |
committer | Gal Paikin <paiking@google.com> | Wed Jan 27 02:22:51 2021 -0500 |
tree | 81ed497ee77f7862e067d28590e33b34be71459b | |
parent | a6b90b7ec5c238692dc323e25ef927e4433edb1d [diff] |
Compare getting all refs except specific refs with seek and with filter There are currently two ways to get all refs except a specific ref, we add two methods that perform both and compare the two different approaches. This change adds two methods that compares the two different approaches of such query: 1. Get all the refs, and then filter by refs that don't start with the prefix (current approach). 2. Get all refs until encountering a ref that is part of the prefix we should exclude, skip using seekPastPrefix, and continue (new approach). This works since the refs are sorted. Specifically in Gerrit, we often have thousands of refs that are not refs/changes, and millions of refs/changes, hence the second approach should be much faster. In Jgit in general it's still expected to provide a better result even if we're skipping a smaller chunk of the refs since the complexity here is O(logn) with a binary search, rather than O(number of skipped refs). We ran this benchmark on a big chunk of chromium/src's reftable. To run it, we first create the reftable: git ls-remote https://chromium.googlesource.com/chromium/src > lsr bazel build org.eclipse.jgit.pgm:jgit && rm -rf /tmp/reftable* && \ ./bazel-bin/org.eclipse.jgit.pgm/jgit debug-benchmark-reftable \ --test write_stack lsr /tmp/reftable Then, we actually test the created reftable. Note that we can't test all of them at once since there are multiple ones, but below is a good example. bazel build org.eclipse.jgit.pgm:jgit && \ ./bazel-bin/org.eclipse.jgit.pgm/jgit debug-benchmark-reftable \ --test get_refs_excluding_ref --ref refs/changes \ lsr /tmp/reftable/000000000001-0000001e0371.ref Result: total time the action took using seek: 36925 usec total time the action took using filter: 874382 usec number of refs that start with prefix: 4266. number of refs that don't start with prefix: 1962695. Similarly for Android's biggest repository, platform/frameworks/base (still only partial result): total time the action took using seek: 9020 usec total time the action took using filter: 143166 usec number of refs that start with prefix: 296. number of refs that don't start with prefix: 60400. In conclusion, it's easy to see an improvement of a factor of 15-20x for large Gerrit repositories! Signed-off-by: Gal Paikin <paiking@google.com> Change-Id: I36d9b63eb259804c774864429cf2c761cd099cc3
An implementation of the Git version control system in pure Java.
This project is licensed under the EDL (Eclipse Distribution License).
JGit can be imported straight into Eclipse and built and tested from there. It can be built from the command line using Maven or Bazel. The CI builds use Maven and run on Jenkins.
org.eclipse.jgit
A pure Java library capable of being run standalone, with no additional support libraries. It provides classes to read and write a Git repository and operate on a working directory.
All portions of JGit are covered by the EDL. Absolutely no GPL, LGPL or EPL contributions are accepted within this package.
org.eclipse.jgit.ant
Ant tasks based on JGit.
org.eclipse.jgit.archive
Support for exporting to various archive formats (zip etc).
org.eclipse.jgit.http.apache
Apache httpclient support.
org.eclipse.jgit.http.server
Server for the smart and dumb Git HTTP protocol.
org.eclipse.jgit.lfs
Support for LFS (Large File Storage).
org.eclipse.jgit.lfs.server
Basic LFS server support.
org.eclipse.jgit.packaging
Production of Eclipse features and p2 repository for JGit. See the JGit Wiki on why and how to use this module.
org.eclipse.jgit.pgm
Command-line interface Git commands implemented using JGit (“pgm” stands for program).
org.eclipse.jgit.ssh.apache
Client support for the ssh protocol based on Apache Mina sshd.
org.eclipse.jgit.ui
Simple UI for displaying git log.
Native symbolic links are supported, provided the file system supports them. For Windows you must use a non-administrator account and have the SeCreateSymbolicLinkPrivilege.
Only the timestamp of the index is used by JGit if the index is dirty.
JGit requires at least a Java 8 JDK.
CRLF conversion is performed depending on the core.autocrlf
setting, however Git for Windows by default stores that setting during installation in the “system wide” configuration file. If Git is not installed, use the global or repository configuration for the core.autocrlf setting.
The system wide configuration file is located relative to where C Git is installed. Make sure Git can be found via the PATH environment variable. When installing Git for Windows check the “Run Git from the Windows Command Prompt” option. There are other options like Eclipse settings that can be used for pointing out where C Git is installed. Modifying PATH is the recommended option if C Git is installed.
We try to use the same notation of $HOME
as C Git does. On Windows this is often not the same value as the user.home
system property.
org.eclipse.jgit
Read loose and packed commits, trees, blobs, including deltafied objects.
Read objects from shared repositories
Write loose commits, trees, blobs.
Write blobs from local files or Java InputStreams.
Read blobs as Java InputStreams.
Copy trees to local directory, or local directory to a tree.
Lazily loads objects as necessary.
Read and write .git/config files.
Create a new repository.
Read and write refs, including walking through symrefs.
Read, update and write the Git index.
Checkout in dirty working directory if trivial.
Walk the history from a given set of commits looking for commits introducing changes in files under a specified path.
Object transport
Fetch via ssh, git, http, Amazon S3 and bundles. Push via ssh, git and Amazon S3. JGit does not yet deltify the pushed packs so they may be a lot larger than C Git packs.
Garbage collection
Merge
Rebase
And much more
org.eclipse.jgit.pgm
org.eclipse.jgit.ant
org.eclipse.jgit.archive
org.eclipse.http
There are some missing features:
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See the EGit Contributor Guide.
More information about Git, its repository format, and the canonical C based implementation can be obtained from the Git website.