##// END OF EJS Templates
snapshot: search for unrelated but reusable full-snapshot...
snapshot: search for unrelated but reusable full-snapshot # New Strategy Step: Reusing Snapshot Outside Of Parents' Chain. If no suitable bases were found in the parent's chains, see if we could reuse a full snapshot not directly related to the current revision. Such search can be expensive, so we only search for snapshots appended to the revlog *after* the bases used by the parents of the current revision (the one we just tested). We assume the parent's bases were created because the previous snapshots were unsuitable, so there are low odds they would be useful now. This search gives a chance to reuse a delta chain unrelated to the current revision. Without this re-use, topological branches would keep reopening new full chains. Creating more and more snapshots as the repository grow. In repositories with many topological branches, the lack of delta reuse can create too many snapshots reducing overall compression to nothing. This results in a very large repository and other usability issues. For now, we still focus on creating level-1 snapshots. However, this principle will play a large part in how we avoid snapshot explosion once we have more snapshot levels. # Effects On The Test Repository In the test repository we created, we can see the beneficial effect of such reuse. We need very few level-0 snapshots and the overall revlog size has decreased. The `hg debugrevlog` call, show a "lvl-2" snapshot. It comes from the existing delta logic using the `prev` revision (revlog's tip) as the base. In this specific case, it turns out the tip was a level-1 snapshot. This is a coincidence that can be ignored. Finding and testing against all these unrelated snapshots can have a performance impact at write time. We currently focus on building good deltas chain we build. Performance concern will be dealt with later in another series.

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diffutil.py
105 lines | 4.3 KiB | text/x-python | PythonLexer
# diffutil.py - utility functions related to diff and patch
#
# Copyright 2006 Brendan Cully <brendan@kublai.com>
# Copyright 2007 Chris Mason <chris.mason@oracle.com>
# Copyright 2018 Octobus <octobus@octobus.net>
#
# 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 . import (
mdiff,
pycompat,
)
def diffallopts(ui, opts=None, untrusted=False, section='diff'):
'''return diffopts with all features supported and parsed'''
return difffeatureopts(ui, opts=opts, untrusted=untrusted, section=section,
git=True, whitespace=True, formatchanging=True)
def difffeatureopts(ui, opts=None, untrusted=False, section='diff', git=False,
whitespace=False, formatchanging=False):
'''return diffopts with only opted-in features parsed
Features:
- git: git-style diffs
- whitespace: whitespace options like ignoreblanklines and ignorews
- formatchanging: options that will likely break or cause correctness issues
with most diff parsers
'''
def get(key, name=None, getter=ui.configbool, forceplain=None):
if opts:
v = opts.get(key)
# diffopts flags are either None-default (which is passed
# through unchanged, so we can identify unset values), or
# some other falsey default (eg --unified, which defaults
# to an empty string). We only want to override the config
# entries from hgrc with command line values if they
# appear to have been set, which is any truthy value,
# True, or False.
if v or isinstance(v, bool):
return v
if forceplain is not None and ui.plain():
return forceplain
return getter(section, name or key, untrusted=untrusted)
# core options, expected to be understood by every diff parser
buildopts = {
'nodates': get('nodates'),
'showfunc': get('show_function', 'showfunc'),
'context': get('unified', getter=ui.config),
}
buildopts['xdiff'] = ui.configbool('experimental', 'xdiff')
if git:
buildopts['git'] = get('git')
# since this is in the experimental section, we need to call
# ui.configbool directory
buildopts['showsimilarity'] = ui.configbool('experimental',
'extendedheader.similarity')
# need to inspect the ui object instead of using get() since we want to
# test for an int
hconf = ui.config('experimental', 'extendedheader.index')
if hconf is not None:
hlen = None
try:
# the hash config could be an integer (for length of hash) or a
# word (e.g. short, full, none)
hlen = int(hconf)
if hlen < 0 or hlen > 40:
msg = _("invalid length for extendedheader.index: '%d'\n")
ui.warn(msg % hlen)
except ValueError:
# default value
if hconf == 'short' or hconf == '':
hlen = 12
elif hconf == 'full':
hlen = 40
elif hconf != 'none':
msg = _("invalid value for extendedheader.index: '%s'\n")
ui.warn(msg % hconf)
finally:
buildopts['index'] = hlen
if whitespace:
buildopts['ignorews'] = get('ignore_all_space', 'ignorews')
buildopts['ignorewsamount'] = get('ignore_space_change',
'ignorewsamount')
buildopts['ignoreblanklines'] = get('ignore_blank_lines',
'ignoreblanklines')
buildopts['ignorewseol'] = get('ignore_space_at_eol', 'ignorewseol')
if formatchanging:
buildopts['text'] = opts and opts.get('text')
binary = None if opts is None else opts.get('binary')
buildopts['nobinary'] = (not binary if binary is not None
else get('nobinary', forceplain=False))
buildopts['noprefix'] = get('noprefix', forceplain=False)
buildopts['worddiff'] = get('word_diff', 'word-diff', forceplain=False)
return mdiff.diffopts(**pycompat.strkwargs(buildopts))