view relnotes/5.2 @ 50337:47686726545d stable

match: sort patterns before compiling them into a regex

While investigating cripping performance for `hg cat` in some context, I
discovered that, for large inputs, building a regex from out of order patterns
result may result in a *much* slower regex and a much slower associated
matcher's performance.

So we are now sorting the patterns to help the regex engine.

There is more to the story as we rely on regexp more than we should. See the
next changeset for details.

Benchmarks
==========

In the following benchmark we are comparing the `hg cat` and `hg files` run
time when matching against the full list of files in the repository. They are
run:
 - without the rust extensions
 - with the standard python enfine (so without re2)

sort vs non-sorted - Before this changeset (3f5137543773)
---------------------------------------------------------

###### hg files ###############################################################
### mercurial-2018-08-01-zstd-sparse-revlog
sorted:      0.230092 seconds
shuffled:    0.234235 seconds    (+1.80%)
### pypy-2018-08-01-zstd-sparse-revlog
sorted:      0.613567 seconds
shuffled:    0.801880 seconds   (+30.69%)
### mozilla-central-2018-08-01-zstd-sparse-revlog
sorted:     62.474221 seconds
shuffled: 1364.180218 seconds (+2083.59%)
### netbeans-2018-08-01-zstd-sparse-revlog
sorted:    21.541828 seconds
shuffled: 172.759857 seconds   (+701.97%)

###### hg cat #################################################################
### mercurial-2018-08-01-zstd-sparse-revlog
sorted:      0.764407 seconds
shuffled:    0.768924 seconds
### pypy-2018-08-01-zstd-sparse-revlog
sorted:      2.065220 seconds
shuffled:    2.276388 seconds  (+10.22%)
### netbeans-2018-08-01-zstd-sparse-revlog
sorted:     40.967983 seconds
shuffled:  216.388709 seconds (+428.19%)
### mozilla-central-2018-08-01-zstd-sparse-revlog
sorted:    105.228510 seconds
shuffled: 1448.722784 seconds (+1276.74%)

sort vs non-sorted - With this changeset
----------------------------------------

###### hg files ###############################################################
### mercurial-2018-08-01-zstd-sparse-revlog
all-list-pattern-sorted:    0.230069
all-list-pattern-shuffled:  0.231165
### pypy-2018-08-01-zstd-sparse-revlog
all-list-pattern-sorted:    0.616799
all-list-pattern-shuffled:  0.616393
### netbeans-2018-08-01-zstd-sparse-revlog
all-list-pattern-sorted:   21.586773
all-list-pattern-shuffled: 21.908197
### mozilla-central-2018-08-01-zstd-sparse-revlog
all-list-pattern-sorted:   61.279490
all-list-pattern-shuffled: 62.473549

###### hg cat #################################################################
### mercurial-2018-08-01-zstd-sparse-revlog
sorted:      0.763883 seconds
shuffled:    0.765848 seconds
### pypy-2018-08-01-zstd-sparse-revlog
sorted:      2.070498 seconds
shuffled:    2.069197 seconds
### netbeans-2018-08-01-zstd-sparse-revlog
sorted:     41.392423 seconds
shuffled:   41.648689 seconds
### mozilla-central-2018-08-01-zstd-sparse-revlog
sorted:    103.315670 seconds
shuffled:  104.369358 seconds

== New Features ==

 * The amend extension supports the `--currentuser` argument.

 * The amend extension supports the `--close-branch` argument.

 * The amend extension supports the `--secret` argument.

 * The uncommit extension supports the `rewrite.update-timestamp` config option.

== New Experimental Features ==


== Bug Fixes  ==


== Backwards Compatibility Changes ==

 * A shell that supports `$(command)`` syntax for command substitution is now
   required for running the test suite. The test runner normally uses
   `sh`, so if that is a shell that doesn't support `$(command)` syntax,
   you can override it by setting `$HGTEST_SHELL` or by passing it to
   `run-tests.py --shell <shell>`.

 * The (experimental) narrow extension's wire protocol changed. If
   you're using it, you'll need to make sure to upgrade server and
   client at the same time.

== Internal API Changes ==