revlog: change generaldelta delta parent heuristic
The old generaldelta heuristic was "if p1 (or p2) was closer than the last full text,
use it, otherwise use prev". This was problematic when a repo contained multiple
branches that were very different. If commits to branch A were pushed, and the
last full text was branch B, it would generate a fulltext. Then if branch B was
pushed, it would generate another fulltext. The problem is that the last
fulltext (and delta'ing against `prev` in general) has no correlation with the
contents of the incoming revision, and therefore will always have degenerate
cases.
According to the blame, that algorithm was chosen to minimize the chain length.
Since there is already code that protects against that (the delta-vs-fulltext
code), and since it has been improved since the original generaldelta algorithm
went in (2011), I believe the chain length criteria will still be preserved.
The new algorithm always diffs against p1 (or p2 if it's closer), unless the
resulting delta will fail the delta-vs-fulltext check, in which case we delta
against prev.
Some before and after stats on manifest.d size.
internal large repo
old heuristic - 2.0 GB
new heuristic - 1.2 GB
mozilla-central
old heuristic - 242 MB
new heuristic - 261 MB
The regression in mozilla central is due to the new heuristic choosing p2r as
the delta when it's closer to the tip. Switching the algorithm to always prefer
p1r brings the size back down (242 MB). This is result of the way in which
mozilla does merges and pushes, and the result could easily swing the other
direction in other repos (depending on if they merge X into Y or Y into X), but
will never be as degenerate as before.
I future patch will address the regression by introducing an optional, even more
aggressive delta heuristic which will knock the mozilla manifest size down
dramatically.
# discovery.py - protocol changeset discovery functions
#
# Copyright 2010 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 __future__ import absolute_import
from .i18n import _
from .node import (
nullid,
short,
)
from . import (
bookmarks,
branchmap,
obsolete,
phases,
setdiscovery,
treediscovery,
util,
)
def findcommonincoming(repo, remote, heads=None, force=False):
"""Return a tuple (common, anyincoming, heads) used to identify the common
subset of nodes between repo and remote.
"common" is a list of (at least) the heads of the common subset.
"anyincoming" is testable as a boolean indicating if any nodes are missing
locally. If remote does not support getbundle, this actually is a list of
roots of the nodes that would be incoming, to be supplied to
changegroupsubset. No code except for pull should be relying on this fact
any longer.
"heads" is either the supplied heads, or else the remote's heads.
If you pass heads and they are all known locally, the response lists just
these heads in "common" and in "heads".
Please use findcommonoutgoing to compute the set of outgoing nodes to give
extensions a good hook into outgoing.
"""
if not remote.capable('getbundle'):
return treediscovery.findcommonincoming(repo, remote, heads, force)
if heads:
allknown = True
knownnode = repo.changelog.hasnode # no nodemap until it is filtered
for h in heads:
if not knownnode(h):
allknown = False
break
if allknown:
return (heads, False, heads)
res = setdiscovery.findcommonheads(repo.ui, repo, remote,
abortwhenunrelated=not force)
common, anyinc, srvheads = res
return (list(common), anyinc, heads or list(srvheads))
class outgoing(object):
'''Represents the set of nodes present in a local repo but not in a
(possibly) remote one.
Members:
missing is a list of all nodes present in local but not in remote.
common is a list of all nodes shared between the two repos.
excluded is the list of missing changeset that shouldn't be sent remotely.
missingheads is the list of heads of missing.
commonheads is the list of heads of common.
The sets are computed on demand from the heads, unless provided upfront
by discovery.'''
def __init__(self, revlog, commonheads, missingheads):
self.commonheads = commonheads
self.missingheads = missingheads
self._revlog = revlog
self._common = None
self._missing = None
self.excluded = []
def _computecommonmissing(self):
sets = self._revlog.findcommonmissing(self.commonheads,
self.missingheads)
self._common, self._missing = sets
@util.propertycache
def common(self):
if self._common is None:
self._computecommonmissing()
return self._common
@util.propertycache
def missing(self):
if self._missing is None:
self._computecommonmissing()
return self._missing
def findcommonoutgoing(repo, other, onlyheads=None, force=False,
commoninc=None, portable=False):
'''Return an outgoing instance to identify the nodes present in repo but
not in other.
If onlyheads is given, only nodes ancestral to nodes in onlyheads
(inclusive) are included. If you already know the local repo's heads,
passing them in onlyheads is faster than letting them be recomputed here.
If commoninc is given, it must be the result of a prior call to
findcommonincoming(repo, other, force) to avoid recomputing it here.
If portable is given, compute more conservative common and missingheads,
to make bundles created from the instance more portable.'''
# declare an empty outgoing object to be filled later
og = outgoing(repo.changelog, None, None)
# get common set if not provided
if commoninc is None:
commoninc = findcommonincoming(repo, other, force=force)
og.commonheads, _any, _hds = commoninc
# compute outgoing
mayexclude = (repo._phasecache.phaseroots[phases.secret] or repo.obsstore)
if not mayexclude:
og.missingheads = onlyheads or repo.heads()
elif onlyheads is None:
# use visible heads as it should be cached
og.missingheads = repo.filtered("served").heads()
og.excluded = [ctx.node() for ctx in repo.set('secret() or extinct()')]
else:
# compute common, missing and exclude secret stuff
sets = repo.changelog.findcommonmissing(og.commonheads, onlyheads)
og._common, allmissing = sets
og._missing = missing = []
og.excluded = excluded = []
for node in allmissing:
ctx = repo[node]
if ctx.phase() >= phases.secret or ctx.extinct():
excluded.append(node)
else:
missing.append(node)
if len(missing) == len(allmissing):
missingheads = onlyheads
else: # update missing heads
missingheads = phases.newheads(repo, onlyheads, excluded)
og.missingheads = missingheads
if portable:
# recompute common and missingheads as if -r<rev> had been given for
# each head of missing, and --base <rev> for each head of the proper
# ancestors of missing
og._computecommonmissing()
cl = repo.changelog
missingrevs = set(cl.rev(n) for n in og._missing)
og._common = set(cl.ancestors(missingrevs)) - missingrevs
commonheads = set(og.commonheads)
og.missingheads = [h for h in og.missingheads if h not in commonheads]
return og
def _headssummary(repo, remote, outgoing):
"""compute a summary of branch and heads status before and after push
return {'branch': ([remoteheads], [newheads], [unsyncedheads])} mapping
- branch: the branch name
- remoteheads: the list of remote heads known locally
None if the branch is new
- newheads: the new remote heads (known locally) with outgoing pushed
- unsyncedheads: the list of remote heads unknown locally.
"""
cl = repo.changelog
headssum = {}
# A. Create set of branches involved in the push.
branches = set(repo[n].branch() for n in outgoing.missing)
remotemap = remote.branchmap()
newbranches = branches - set(remotemap)
branches.difference_update(newbranches)
# A. register remote heads
remotebranches = set()
for branch, heads in remote.branchmap().iteritems():
remotebranches.add(branch)
known = []
unsynced = []
knownnode = cl.hasnode # do not use nodemap until it is filtered
for h in heads:
if knownnode(h):
known.append(h)
else:
unsynced.append(h)
headssum[branch] = (known, list(known), unsynced)
# B. add new branch data
missingctx = list(repo[n] for n in outgoing.missing)
touchedbranches = set()
for ctx in missingctx:
branch = ctx.branch()
touchedbranches.add(branch)
if branch not in headssum:
headssum[branch] = (None, [], [])
# C drop data about untouched branches:
for branch in remotebranches - touchedbranches:
del headssum[branch]
# D. Update newmap with outgoing changes.
# This will possibly add new heads and remove existing ones.
newmap = branchmap.branchcache((branch, heads[1])
for branch, heads in headssum.iteritems()
if heads[0] is not None)
newmap.update(repo, (ctx.rev() for ctx in missingctx))
for branch, newheads in newmap.iteritems():
headssum[branch][1][:] = newheads
return headssum
def _oldheadssummary(repo, remoteheads, outgoing, inc=False):
"""Compute branchmapsummary for repo without branchmap support"""
# 1-4b. old servers: Check for new topological heads.
# Construct {old,new}map with branch = None (topological branch).
# (code based on update)
knownnode = repo.changelog.hasnode # no nodemap until it is filtered
oldheads = set(h for h in remoteheads if knownnode(h))
# all nodes in outgoing.missing are children of either:
# - an element of oldheads
# - another element of outgoing.missing
# - nullrev
# This explains why the new head are very simple to compute.
r = repo.set('heads(%ln + %ln)', oldheads, outgoing.missing)
newheads = list(c.node() for c in r)
# set some unsynced head to issue the "unsynced changes" warning
if inc:
unsynced = set([None])
else:
unsynced = set()
return {None: (oldheads, newheads, unsynced)}
def checkheads(repo, remote, outgoing, remoteheads, newbranch=False, inc=False,
newbookmarks=[]):
"""Check that a push won't add any outgoing head
raise Abort error and display ui message as needed.
"""
# Check for each named branch if we're creating new remote heads.
# To be a remote head after push, node must be either:
# - unknown locally
# - a local outgoing head descended from update
# - a remote head that's known locally and not
# ancestral to an outgoing head
if remoteheads == [nullid]:
# remote is empty, nothing to check.
return
if remote.capable('branchmap'):
headssum = _headssummary(repo, remote, outgoing)
else:
headssum = _oldheadssummary(repo, remoteheads, outgoing, inc)
newbranches = [branch for branch, heads in headssum.iteritems()
if heads[0] is None]
# 1. Check for new branches on the remote.
if newbranches and not newbranch: # new branch requires --new-branch
branchnames = ', '.join(sorted(newbranches))
raise util.Abort(_("push creates new remote branches: %s!")
% branchnames,
hint=_("use 'hg push --new-branch' to create"
" new remote branches"))
# 2. Compute newly pushed bookmarks. We don't warn about bookmarked heads.
localbookmarks = repo._bookmarks
remotebookmarks = remote.listkeys('bookmarks')
bookmarkedheads = set()
for bm in localbookmarks:
rnode = remotebookmarks.get(bm)
if rnode and rnode in repo:
lctx, rctx = repo[bm], repo[rnode]
if bookmarks.validdest(repo, rctx, lctx):
bookmarkedheads.add(lctx.node())
else:
if bm in newbookmarks:
bookmarkedheads.add(repo[bm].node())
# 3. Check for new heads.
# If there are more heads after the push than before, a suitable
# error message, depending on unsynced status, is displayed.
error = None
# If there is no obsstore, allfuturecommon won't be used, so no
# need to compute it.
if repo.obsstore:
allmissing = set(outgoing.missing)
cctx = repo.set('%ld', outgoing.common)
allfuturecommon = set(c.node() for c in cctx)
allfuturecommon.update(allmissing)
for branch, heads in sorted(headssum.iteritems()):
remoteheads, newheads, unsyncedheads = heads
candidate_newhs = set(newheads)
# add unsynced data
if remoteheads is None:
oldhs = set()
else:
oldhs = set(remoteheads)
oldhs.update(unsyncedheads)
candidate_newhs.update(unsyncedheads)
dhs = None # delta heads, the new heads on branch
discardedheads = set()
if repo.obsstore:
# remove future heads which are actually obsoleted by another
# pushed element:
#
# XXX as above, There are several cases this case does not handle
# XXX properly
#
# (1) if <nh> is public, it won't be affected by obsolete marker
# and a new is created
#
# (2) if the new heads have ancestors which are not obsolete and
# not ancestors of any other heads we will have a new head too.
#
# These two cases will be easy to handle for known changeset but
# much more tricky for unsynced changes.
newhs = set()
for nh in candidate_newhs:
if nh in repo and repo[nh].phase() <= phases.public:
newhs.add(nh)
else:
for suc in obsolete.allsuccessors(repo.obsstore, [nh]):
if suc != nh and suc in allfuturecommon:
discardedheads.add(nh)
break
else:
newhs.add(nh)
else:
newhs = candidate_newhs
unsynced = sorted(h for h in unsyncedheads if h not in discardedheads)
if unsynced:
if None in unsynced:
# old remote, no heads data
heads = None
elif len(unsynced) <= 4 or repo.ui.verbose:
heads = ' '.join(short(h) for h in unsynced)
else:
heads = (' '.join(short(h) for h in unsynced[:4]) +
' ' + _("and %s others") % (len(unsynced) - 4))
if heads is None:
repo.ui.status(_("remote has heads that are "
"not known locally\n"))
elif branch is None:
repo.ui.status(_("remote has heads that are "
"not known locally: %s\n") % heads)
else:
repo.ui.status(_("remote has heads on branch '%s' that are "
"not known locally: %s\n") % (branch, heads))
if remoteheads is None:
if len(newhs) > 1:
dhs = list(newhs)
if error is None:
error = (_("push creates new branch '%s' "
"with multiple heads") % (branch))
hint = _("merge or"
" see \"hg help push\" for details about"
" pushing new heads")
elif len(newhs) > len(oldhs):
# remove bookmarked or existing remote heads from the new heads list
dhs = sorted(newhs - bookmarkedheads - oldhs)
if dhs:
if error is None:
if branch not in ('default', None):
error = _("push creates new remote head %s "
"on branch '%s'!") % (short(dhs[0]), branch)
elif repo[dhs[0]].bookmarks():
error = _("push creates new remote head %s "
"with bookmark '%s'!") % (
short(dhs[0]), repo[dhs[0]].bookmarks()[0])
else:
error = _("push creates new remote head %s!"
) % short(dhs[0])
if unsyncedheads:
hint = _("pull and merge or"
" see \"hg help push\" for details about"
" pushing new heads")
else:
hint = _("merge or"
" see \"hg help push\" for details about"
" pushing new heads")
if branch is None:
repo.ui.note(_("new remote heads:\n"))
else:
repo.ui.note(_("new remote heads on branch '%s':\n") % branch)
for h in dhs:
repo.ui.note((" %s\n") % short(h))
if error:
raise util.Abort(error, hint=hint)