Re: [PATCH] namespace: fastpath name lookup on invalid name

[Yuya Nishihara]

On Thu, 22 Feb 2018 20:33:36 +0100, Boris Feld wrote:
> # HG changeset patch
> # User Boris Feld 
> # Date 1519313522 -3600
> #  Thu Feb 22 16:32:02 2018 +0100
> # Node ID b65a85952c09cf4c71a1458fbc4ec77c49683314
> # Parent  428de1a59f2df3d6d07ff1d7164c8ee56cbb7825
> # EXP-Topic noname
> # Available At https://bitbucket.org/octobus/mercurial-devel/
> #  hg pull https://bitbucket.org/octobus/mercurial-devel/ -r 
> b65a85952c09
> namespace: fastpath name lookup on invalid name
> 
> Since label cannot contains leading or trailing whitespace we can skip looking
> for them. This is useful in repositories with slow labels (eg: special type of
> tags). Short command running on a specific revision can benefit from such
> shortcut.
> 
> eg on a repository where loading tags take 0.4s:
> 
> 1: hg log --template '{node}\n' --rev 'rev(0)'
>0.560 seconds
> 
> 2: hg log --template '{node}\n' --rev ' rev(0)'
>0.109 seconds
> 
> The changeset introduce a generic way to do such fast-pathing to help
> extensions writer to apply the same principle to their extensions.

So is this basically the same as the previous version in that we have to
suggest using a weird syntax (leading/trailing space) to get to the fast path?

https://www.mercurial-scm.org/pipermail/mercurial-devel/2018-February/111432.html
> Instead, maybe we can make lookup() to not search slow labels assuming these
> labeling schemes didn't exist in pre-revset era. Alternatively, we could add
> a config knob to switch off the old-style range support.
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[PATCH] namespace: fastpath name lookup on invalid name

[Boris Feld]

# HG changeset patch
# User Boris Feld 
# Date 1519313522 -3600
#  Thu Feb 22 16:32:02 2018 +0100
# Node ID b65a85952c09cf4c71a1458fbc4ec77c49683314
# Parent  428de1a59f2df3d6d07ff1d7164c8ee56cbb7825
# EXP-Topic noname
# Available At https://bitbucket.org/octobus/mercurial-devel/
#  hg pull https://bitbucket.org/octobus/mercurial-devel/ -r 
b65a85952c09
namespace: fastpath name lookup on invalid name

Since label cannot contains leading or trailing whitespace we can skip looking
for them. This is useful in repositories with slow labels (eg: special type of
tags). Short command running on a specific revision can benefit from such
shortcut.

eg on a repository where loading tags take 0.4s:

1: hg log --template '{node}\n' --rev 'rev(0)'
   0.560 seconds

2: hg log --template '{node}\n' --rev ' rev(0)'
   0.109 seconds

The changeset introduce a generic way to do such fast-pathing to help
extensions writer to apply the same principle to their extensions.

diff --git a/mercurial/namespaces.py b/mercurial/namespaces.py
--- a/mercurial/namespaces.py
+++ b/mercurial/namespaces.py
@@ -1,5 +1,7 @@
 from __future__ import absolute_import
 
+import re
+
 from .i18n import _
 from . import (
 templatekw,
@@ -15,6 +17,23 @@ def tolist(val):
 else:
 return [val]
 
+def lazynamemap(regexp, function):
+"""wrap a namemap function in order to call it only if the name matches a
+regexp
+"""
+namefilter = re.compile(regexp)
+
+def namemap(repo, name):
+if namefilter.match(name):
+return function(repo, name)
+return []
+return namemap
+
+# no ":", "\n", "\0", "\r" within the name, no " " around it.
+commonfilter = b'^[^ :\0\r\n]+([^:\0\r\n]*[^ :\0\r\n]+)?$'
+# at some point we allowed ":" in branch names.
+branchfilter = b'^[^ \0\r\n]+([^\0\r\n]*[^ \0\r\n]+)?$'
+
 class namespaces(object):
 """provides an interface to register and operate on multiple namespaces. 
See
 the namespace class below for details on the namespace object.
@@ -30,7 +49,8 @@ class namespaces(object):
 # we need current mercurial named objects (bookmarks, tags, and
 # branches) to be initialized somewhere, so that place is here
 bmknames = lambda repo: repo._bookmarks.keys()
-bmknamemap = lambda repo, name: tolist(repo._bookmarks.get(name))
+_bmknamemap = lambda repo, name: tolist(repo._bookmarks.get(name))
+bmknamemap = lazynamemap(commonfilter, _bmknamemap)
 bmknodemap = lambda repo, node: repo.nodebookmarks(node)
 n = namespace("bookmarks", templatename="bookmark",
   logfmt=columns['bookmark'],
@@ -40,7 +60,8 @@ class namespaces(object):
 self.addnamespace(n)
 
 tagnames = lambda repo: [t for t, n in repo.tagslist()]
-tagnamemap = lambda repo, name: tolist(repo._tagscache.tags.get(name))
+_tagnamemap = lambda repo, name: tolist(repo._tagscache.tags.get(name))
+tagnamemap = lazynamemap(commonfilter, _tagnamemap)
 tagnodemap = lambda repo, node: repo.nodetags(node)
 n = namespace("tags", templatename="tag",
   logfmt=columns['tag'],
@@ -51,7 +72,8 @@ class namespaces(object):
 self.addnamespace(n)
 
 bnames = lambda repo: repo.branchmap().keys()
-bnamemap = lambda repo, name: tolist(repo.branchtip(name, True))
+_bnamemap = lambda repo, name: tolist(repo.branchtip(name, True))
+bnamemap = lazynamemap(branchfilter, _bnamemap)
 bnodemap = lambda repo, node: [repo[node].branch()]
 n = namespace("branches", templatename="branch",
   logfmt=columns['branch'],
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