Mercurial > hg
view mercurial/statichttprepo.py @ 18040:fe8caf28d580
strip: make query to get new bookmark target cheaper
The current query to get the new bookmark target for stripped revisions
involves multiple walks up the DAG, and is really expensive, taking over 2.5
seconds on a repository with over 400,000 changesets even if just one
changeset is being stripped.
A slightly simplified version of the current query is
max(heads(::<tostrip> - <tostrip>))
We make two observations here.
1. For any set s, max(heads(s)) == max(s). That is because revision numbers
define a topological order, so that the element with the highest revision
number in s will not have any children in s.
2. For any set s, max(::s - s) == max(parents(s) - s). In other words, the
ancestor of s with the highest revision number not in s is a parent of one
of the revs in s. Why? Because if it were an ancestor but not a parent of s,
it would have a descendant that would be a parent of s. This descendant
would have a higher revision number, leading to a contradiction.
Combining these two observations, we rewrite the revset query as
max(parents(<tostrip>) - <tostrip>)
The time complexity is now linear in the number of changesets being stripped.
For the above repository, the query now takes 0.1 seconds when one changeset
is stripped. This speeds up operations that use repair.strip, like the rebase
and strip commands.
author | Siddharth Agarwal <sid0@fb.com> |
---|---|
date | Wed, 05 Dec 2012 14:33:15 -0800 |
parents | ffd589d4b785 |
children | ad194a8ab5c1 |
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# statichttprepo.py - simple http repository class for mercurial # # This provides read-only repo access to repositories exported via static http # # Copyright 2005-2007 Matt Mackall <mpm@selenic.com> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. from i18n import _ import changelog, byterange, url, error import localrepo, manifest, util, scmutil, store import urllib, urllib2, errno class httprangereader(object): def __init__(self, url, opener): # we assume opener has HTTPRangeHandler self.url = url self.pos = 0 self.opener = opener self.name = url def seek(self, pos): self.pos = pos def read(self, bytes=None): req = urllib2.Request(self.url) end = '' if bytes: end = self.pos + bytes - 1 if self.pos or end: req.add_header('Range', 'bytes=%d-%s' % (self.pos, end)) try: f = self.opener.open(req) data = f.read() # Python 2.6+ defines a getcode() function, and 2.4 and # 2.5 appear to always have an undocumented code attribute # set. If we can't read either of those, fall back to 206 # and hope for the best. code = getattr(f, 'getcode', lambda : getattr(f, 'code', 206))() except urllib2.HTTPError, inst: num = inst.code == 404 and errno.ENOENT or None raise IOError(num, inst) except urllib2.URLError, inst: raise IOError(None, inst.reason[1]) if code == 200: # HTTPRangeHandler does nothing if remote does not support # Range headers and returns the full entity. Let's slice it. if bytes: data = data[self.pos:self.pos + bytes] else: data = data[self.pos:] elif bytes: data = data[:bytes] self.pos += len(data) return data def __iter__(self): return iter(self.read().splitlines(1)) def close(self): pass def build_opener(ui, authinfo): # urllib cannot handle URLs with embedded user or passwd urlopener = url.opener(ui, authinfo) urlopener.add_handler(byterange.HTTPRangeHandler()) class statichttpvfs(scmutil.abstractvfs): def __init__(self, base): self.base = base def __call__(self, path, mode="r", atomictemp=None): if mode not in ('r', 'rb'): raise IOError('Permission denied') f = "/".join((self.base, urllib.quote(path))) return httprangereader(f, urlopener) def join(self, path): if path: return os.path.join(self.base, path) else: return self.base return statichttpvfs class statichttppeer(localrepo.localpeer): def local(self): return None def canpush(self): return False class statichttprepository(localrepo.localrepository): def __init__(self, ui, path): self._url = path self.ui = ui self.root = path u = util.url(path.rstrip('/') + "/.hg") self.path, authinfo = u.authinfo() opener = build_opener(ui, authinfo) self.opener = opener(self.path) self.vfs = self.opener self._phasedefaults = [] try: requirements = scmutil.readrequires(self.opener, self.supported) except IOError, inst: if inst.errno != errno.ENOENT: raise requirements = set() # check if it is a non-empty old-style repository try: fp = self.opener("00changelog.i") fp.read(1) fp.close() except IOError, inst: if inst.errno != errno.ENOENT: raise # we do not care about empty old-style repositories here msg = _("'%s' does not appear to be an hg repository") % path raise error.RepoError(msg) # setup store self.store = store.store(requirements, self.path, opener) self.spath = self.store.path self.sopener = self.store.opener self.svfs = self.sopener self.sjoin = self.store.join self._filecache = {} self.requirements = requirements self.manifest = manifest.manifest(self.sopener) self.changelog = changelog.changelog(self.sopener) self._tags = None self.nodetagscache = None self._branchcache = None self._branchcachetip = None self.encodepats = None self.decodepats = None def _restrictcapabilities(self, caps): return caps.difference(["pushkey"]) def url(self): return self._url def local(self): return False def peer(self): return statichttppeer(self) def lock(self, wait=True): raise util.Abort(_('cannot lock static-http repository')) def instance(ui, path, create): if create: raise util.Abort(_('cannot create new static-http repository')) return statichttprepository(ui, path[7:])