##// 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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config.py
280 lines | 9.9 KiB | text/x-python | PythonLexer
# config.py - configuration parsing for Mercurial
#
# Copyright 2009 Matt Mackall <mpm@selenic.com> and others
#
# 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
import errno
import os
from .i18n import _
from . import (
error,
pycompat,
util,
)
class config(object):
def __init__(self, data=None, includepaths=None):
self._data = {}
self._unset = []
self._includepaths = includepaths or []
if data:
for k in data._data:
self._data[k] = data[k].copy()
self._source = data._source.copy()
else:
self._source = util.cowdict()
def copy(self):
return config(self)
def __contains__(self, section):
return section in self._data
def hasitem(self, section, item):
return item in self._data.get(section, {})
def __getitem__(self, section):
return self._data.get(section, {})
def __iter__(self):
for d in self.sections():
yield d
def update(self, src):
self._source = self._source.preparewrite()
for s, n in src._unset:
ds = self._data.get(s, None)
if ds is not None and n in ds:
self._data[s] = ds.preparewrite()
del self._data[s][n]
del self._source[(s, n)]
for s in src:
ds = self._data.get(s, None)
if ds:
self._data[s] = ds.preparewrite()
else:
self._data[s] = util.cowsortdict()
self._data[s].update(src._data[s])
self._source.update(src._source)
def get(self, section, item, default=None):
return self._data.get(section, {}).get(item, default)
def backup(self, section, item):
"""return a tuple allowing restore to reinstall a previous value
The main reason we need it is because it handles the "no data" case.
"""
try:
value = self._data[section][item]
source = self.source(section, item)
return (section, item, value, source)
except KeyError:
return (section, item)
def source(self, section, item):
return self._source.get((section, item), "")
def sections(self):
return sorted(self._data.keys())
def items(self, section):
return list(self._data.get(section, {}).iteritems())
def set(self, section, item, value, source=""):
if pycompat.ispy3:
assert not isinstance(value, str), (
'config values may not be unicode strings on Python 3')
if section not in self:
self._data[section] = util.cowsortdict()
else:
self._data[section] = self._data[section].preparewrite()
self._data[section][item] = value
if source:
self._source = self._source.preparewrite()
self._source[(section, item)] = source
def restore(self, data):
"""restore data returned by self.backup"""
self._source = self._source.preparewrite()
if len(data) == 4:
# restore old data
section, item, value, source = data
self._data[section] = self._data[section].preparewrite()
self._data[section][item] = value
self._source[(section, item)] = source
else:
# no data before, remove everything
section, item = data
if section in self._data:
self._data[section].pop(item, None)
self._source.pop((section, item), None)
def parse(self, src, data, sections=None, remap=None, include=None):
sectionre = util.re.compile(br'\[([^\[]+)\]')
itemre = util.re.compile(br'([^=\s][^=]*?)\s*=\s*(.*\S|)')
contre = util.re.compile(br'\s+(\S|\S.*\S)\s*$')
emptyre = util.re.compile(br'(;|#|\s*$)')
commentre = util.re.compile(br'(;|#)')
unsetre = util.re.compile(br'%unset\s+(\S+)')
includere = util.re.compile(br'%include\s+(\S|\S.*\S)\s*$')
section = ""
item = None
line = 0
cont = False
if remap:
section = remap.get(section, section)
for l in data.splitlines(True):
line += 1
if line == 1 and l.startswith('\xef\xbb\xbf'):
# Someone set us up the BOM
l = l[3:]
if cont:
if commentre.match(l):
continue
m = contre.match(l)
if m:
if sections and section not in sections:
continue
v = self.get(section, item) + "\n" + m.group(1)
self.set(section, item, v, "%s:%d" % (src, line))
continue
item = None
cont = False
m = includere.match(l)
if m and include:
expanded = util.expandpath(m.group(1))
includepaths = [os.path.dirname(src)] + self._includepaths
for base in includepaths:
inc = os.path.normpath(os.path.join(base, expanded))
try:
include(inc, remap=remap, sections=sections)
break
except IOError as inst:
if inst.errno != errno.ENOENT:
raise error.ParseError(_("cannot include %s (%s)")
% (inc, inst.strerror),
"%s:%d" % (src, line))
continue
if emptyre.match(l):
continue
m = sectionre.match(l)
if m:
section = m.group(1)
if remap:
section = remap.get(section, section)
if section not in self:
self._data[section] = util.cowsortdict()
continue
m = itemre.match(l)
if m:
item = m.group(1)
cont = True
if sections and section not in sections:
continue
self.set(section, item, m.group(2), "%s:%d" % (src, line))
continue
m = unsetre.match(l)
if m:
name = m.group(1)
if sections and section not in sections:
continue
if self.get(section, name) is not None:
self._data[section] = self._data[section].preparewrite()
del self._data[section][name]
self._unset.append((section, name))
continue
raise error.ParseError(l.rstrip(), ("%s:%d" % (src, line)))
def read(self, path, fp=None, sections=None, remap=None):
if not fp:
fp = util.posixfile(path, 'rb')
assert getattr(fp, 'mode', r'rb') == r'rb', (
'config files must be opened in binary mode, got fp=%r mode=%r' % (
fp, fp.mode))
self.parse(path, fp.read(),
sections=sections, remap=remap, include=self.read)
def parselist(value):
"""parse a configuration value as a list of comma/space separated strings
>>> parselist(b'this,is "a small" ,test')
['this', 'is', 'a small', 'test']
"""
def _parse_plain(parts, s, offset):
whitespace = False
while offset < len(s) and (s[offset:offset + 1].isspace()
or s[offset:offset + 1] == ','):
whitespace = True
offset += 1
if offset >= len(s):
return None, parts, offset
if whitespace:
parts.append('')
if s[offset:offset + 1] == '"' and not parts[-1]:
return _parse_quote, parts, offset + 1
elif s[offset:offset + 1] == '"' and parts[-1][-1:] == '\\':
parts[-1] = parts[-1][:-1] + s[offset:offset + 1]
return _parse_plain, parts, offset + 1
parts[-1] += s[offset:offset + 1]
return _parse_plain, parts, offset + 1
def _parse_quote(parts, s, offset):
if offset < len(s) and s[offset:offset + 1] == '"': # ""
parts.append('')
offset += 1
while offset < len(s) and (s[offset:offset + 1].isspace() or
s[offset:offset + 1] == ','):
offset += 1
return _parse_plain, parts, offset
while offset < len(s) and s[offset:offset + 1] != '"':
if (s[offset:offset + 1] == '\\' and offset + 1 < len(s)
and s[offset + 1:offset + 2] == '"'):
offset += 1
parts[-1] += '"'
else:
parts[-1] += s[offset:offset + 1]
offset += 1
if offset >= len(s):
real_parts = _configlist(parts[-1])
if not real_parts:
parts[-1] = '"'
else:
real_parts[0] = '"' + real_parts[0]
parts = parts[:-1]
parts.extend(real_parts)
return None, parts, offset
offset += 1
while offset < len(s) and s[offset:offset + 1] in [' ', ',']:
offset += 1
if offset < len(s):
if offset + 1 == len(s) and s[offset:offset + 1] == '"':
parts[-1] += '"'
offset += 1
else:
parts.append('')
else:
return None, parts, offset
return _parse_plain, parts, offset
def _configlist(s):
s = s.rstrip(' ,')
if not s:
return []
parser, parts, offset = _parse_plain, [''], 0
while parser:
parser, parts, offset = parser(parts, s, offset)
return parts
if value is not None and isinstance(value, bytes):
result = _configlist(value.lstrip(' ,\n'))
else:
result = value
return result or []