Mercurial > hg
view mercurial/revlogutils/deltas.py @ 39487:931386a0b108
revlog: drop duplicated code
This code probably got duplicated by a rebase/evolve conflict. We drop the
extra copy, the other copy is right below.
This had no real effects since other logic ensure that we never test the same
revision twice.
author | Boris Feld <boris.feld@octobus.net> |
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date | Tue, 04 Sep 2018 21:05:21 +0200 |
parents | 37957e07138c |
children | d629b6d2f05a |
line wrap: on
line source
# revlogdeltas.py - Logic around delta computation for revlog # # Copyright 2005-2007 Matt Mackall <mpm@selenic.com> # Copyright 2018 Octobus <contact@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. """Helper class to compute deltas stored inside revlogs""" from __future__ import absolute_import import heapq import struct # import stuff from node for others to import from revlog from ..node import ( nullrev, ) from ..i18n import _ from .constants import ( REVIDX_ISCENSORED, REVIDX_RAWTEXT_CHANGING_FLAGS, ) from ..thirdparty import ( attr, ) from .. import ( error, mdiff, ) RevlogError = error.RevlogError CensoredNodeError = error.CensoredNodeError # maximum <delta-chain-data>/<revision-text-length> ratio LIMIT_DELTA2TEXT = 2 class _testrevlog(object): """minimalist fake revlog to use in doctests""" def __init__(self, data, density=0.5, mingap=0): """data is an list of revision payload boundaries""" self._data = data self._srdensitythreshold = density self._srmingapsize = mingap def start(self, rev): if rev == 0: return 0 return self._data[rev - 1] def end(self, rev): return self._data[rev] def length(self, rev): return self.end(rev) - self.start(rev) def __len__(self): return len(self._data) def slicechunk(revlog, revs, deltainfo=None, targetsize=None): """slice revs to reduce the amount of unrelated data to be read from disk. ``revs`` is sliced into groups that should be read in one time. Assume that revs are sorted. The initial chunk is sliced until the overall density (payload/chunks-span ratio) is above `revlog._srdensitythreshold`. No gap smaller than `revlog._srmingapsize` is skipped. If `targetsize` is set, no chunk larger than `targetsize` will be yield. For consistency with other slicing choice, this limit won't go lower than `revlog._srmingapsize`. If individual revisions chunk are larger than this limit, they will still be raised individually. >>> revlog = _testrevlog([ ... 5, #00 (5) ... 10, #01 (5) ... 12, #02 (2) ... 12, #03 (empty) ... 27, #04 (15) ... 31, #05 (4) ... 31, #06 (empty) ... 42, #07 (11) ... 47, #08 (5) ... 47, #09 (empty) ... 48, #10 (1) ... 51, #11 (3) ... 74, #12 (23) ... 85, #13 (11) ... 86, #14 (1) ... 91, #15 (5) ... ]) >>> list(slicechunk(revlog, list(range(16)))) [[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]] >>> list(slicechunk(revlog, [0, 15])) [[0], [15]] >>> list(slicechunk(revlog, [0, 11, 15])) [[0], [11], [15]] >>> list(slicechunk(revlog, [0, 11, 13, 15])) [[0], [11, 13, 15]] >>> list(slicechunk(revlog, [1, 2, 3, 5, 8, 10, 11, 14])) [[1, 2], [5, 8, 10, 11], [14]] Slicing with a maximum chunk size >>> list(slicechunk(revlog, [0, 11, 13, 15], targetsize=15)) [[0], [11], [13], [15]] >>> list(slicechunk(revlog, [0, 11, 13, 15], targetsize=20)) [[0], [11], [13, 15]] """ if targetsize is not None: targetsize = max(targetsize, revlog._srmingapsize) # targetsize should not be specified when evaluating delta candidates: # * targetsize is used to ensure we stay within specification when reading, # * deltainfo is used to pick are good delta chain when writing. if not (deltainfo is None or targetsize is None): msg = 'cannot use `targetsize` with a `deltainfo`' raise error.ProgrammingError(msg) for chunk in _slicechunktodensity(revlog, revs, deltainfo, revlog._srdensitythreshold, revlog._srmingapsize): for subchunk in _slicechunktosize(revlog, chunk, targetsize): yield subchunk def _slicechunktosize(revlog, revs, targetsize=None): """slice revs to match the target size This is intended to be used on chunk that density slicing selected by that are still too large compared to the read garantee of revlog. This might happens when "minimal gap size" interrupted the slicing or when chain are built in a way that create large blocks next to each other. >>> revlog = _testrevlog([ ... 3, #0 (3) ... 5, #1 (2) ... 6, #2 (1) ... 8, #3 (2) ... 8, #4 (empty) ... 11, #5 (3) ... 12, #6 (1) ... 13, #7 (1) ... 14, #8 (1) ... ]) Cases where chunk is already small enough >>> list(_slicechunktosize(revlog, [0], 3)) [[0]] >>> list(_slicechunktosize(revlog, [6, 7], 3)) [[6, 7]] >>> list(_slicechunktosize(revlog, [0], None)) [[0]] >>> list(_slicechunktosize(revlog, [6, 7], None)) [[6, 7]] cases where we need actual slicing >>> list(_slicechunktosize(revlog, [0, 1], 3)) [[0], [1]] >>> list(_slicechunktosize(revlog, [1, 3], 3)) [[1], [3]] >>> list(_slicechunktosize(revlog, [1, 2, 3], 3)) [[1, 2], [3]] >>> list(_slicechunktosize(revlog, [3, 5], 3)) [[3], [5]] >>> list(_slicechunktosize(revlog, [3, 4, 5], 3)) [[3], [5]] >>> list(_slicechunktosize(revlog, [5, 6, 7, 8], 3)) [[5], [6, 7, 8]] >>> list(_slicechunktosize(revlog, [0, 1, 2, 3, 4, 5, 6, 7, 8], 3)) [[0], [1, 2], [3], [5], [6, 7, 8]] Case with too large individual chunk (must return valid chunk) >>> list(_slicechunktosize(revlog, [0, 1], 2)) [[0], [1]] >>> list(_slicechunktosize(revlog, [1, 3], 1)) [[1], [3]] >>> list(_slicechunktosize(revlog, [3, 4, 5], 2)) [[3], [5]] """ assert targetsize is None or 0 <= targetsize if targetsize is None or segmentspan(revlog, revs) <= targetsize: yield revs return startrevidx = 0 startdata = revlog.start(revs[0]) endrevidx = 0 iterrevs = enumerate(revs) next(iterrevs) # skip first rev. for idx, r in iterrevs: span = revlog.end(r) - startdata if span <= targetsize: endrevidx = idx else: chunk = _trimchunk(revlog, revs, startrevidx, endrevidx + 1) if chunk: yield chunk startrevidx = idx startdata = revlog.start(r) endrevidx = idx yield _trimchunk(revlog, revs, startrevidx) def _slicechunktodensity(revlog, revs, deltainfo=None, targetdensity=0.5, mingapsize=0): """slice revs to reduce the amount of unrelated data to be read from disk. ``revs`` is sliced into groups that should be read in one time. Assume that revs are sorted. ``deltainfo`` is a _deltainfo instance of a revision that we would append to the top of the revlog. The initial chunk is sliced until the overall density (payload/chunks-span ratio) is above `targetdensity`. No gap smaller than `mingapsize` is skipped. >>> revlog = _testrevlog([ ... 5, #00 (5) ... 10, #01 (5) ... 12, #02 (2) ... 12, #03 (empty) ... 27, #04 (15) ... 31, #05 (4) ... 31, #06 (empty) ... 42, #07 (11) ... 47, #08 (5) ... 47, #09 (empty) ... 48, #10 (1) ... 51, #11 (3) ... 74, #12 (23) ... 85, #13 (11) ... 86, #14 (1) ... 91, #15 (5) ... ]) >>> list(_slicechunktodensity(revlog, list(range(16)))) [[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]] >>> list(_slicechunktodensity(revlog, [0, 15])) [[0], [15]] >>> list(_slicechunktodensity(revlog, [0, 11, 15])) [[0], [11], [15]] >>> list(_slicechunktodensity(revlog, [0, 11, 13, 15])) [[0], [11, 13, 15]] >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14])) [[1, 2], [5, 8, 10, 11], [14]] >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14], ... mingapsize=20)) [[1, 2, 3, 5, 8, 10, 11], [14]] >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14], ... targetdensity=0.95)) [[1, 2], [5], [8, 10, 11], [14]] >>> list(_slicechunktodensity(revlog, [1, 2, 3, 5, 8, 10, 11, 14], ... targetdensity=0.95, mingapsize=12)) [[1, 2], [5, 8, 10, 11], [14]] """ start = revlog.start length = revlog.length if len(revs) <= 1: yield revs return nextrev = len(revlog) nextoffset = revlog.end(nextrev - 1) if deltainfo is None: deltachainspan = segmentspan(revlog, revs) chainpayload = sum(length(r) for r in revs) else: deltachainspan = deltainfo.distance chainpayload = deltainfo.compresseddeltalen if deltachainspan < mingapsize: yield revs return readdata = deltachainspan if deltachainspan: density = chainpayload / float(deltachainspan) else: density = 1.0 if density >= targetdensity: yield revs return if deltainfo is not None and deltainfo.deltalen: revs = list(revs) revs.append(nextrev) # Store the gaps in a heap to have them sorted by decreasing size gapsheap = [] heapq.heapify(gapsheap) prevend = None for i, rev in enumerate(revs): if rev < nextrev: revstart = start(rev) revlen = length(rev) else: revstart = nextoffset revlen = deltainfo.deltalen # Skip empty revisions to form larger holes if revlen == 0: continue if prevend is not None: gapsize = revstart - prevend # only consider holes that are large enough if gapsize > mingapsize: heapq.heappush(gapsheap, (-gapsize, i)) prevend = revstart + revlen # Collect the indices of the largest holes until the density is acceptable indicesheap = [] heapq.heapify(indicesheap) while gapsheap and density < targetdensity: oppgapsize, gapidx = heapq.heappop(gapsheap) heapq.heappush(indicesheap, gapidx) # the gap sizes are stored as negatives to be sorted decreasingly # by the heap readdata -= (-oppgapsize) if readdata > 0: density = chainpayload / float(readdata) else: density = 1.0 # Cut the revs at collected indices previdx = 0 while indicesheap: idx = heapq.heappop(indicesheap) chunk = _trimchunk(revlog, revs, previdx, idx) if chunk: yield chunk previdx = idx chunk = _trimchunk(revlog, revs, previdx) if chunk: yield chunk def _trimchunk(revlog, revs, startidx, endidx=None): """returns revs[startidx:endidx] without empty trailing revs Doctest Setup >>> revlog = _testrevlog([ ... 5, #0 ... 10, #1 ... 12, #2 ... 12, #3 (empty) ... 17, #4 ... 21, #5 ... 21, #6 (empty) ... ]) Contiguous cases: >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 0) [0, 1, 2, 3, 4, 5] >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 0, 5) [0, 1, 2, 3, 4] >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 0, 4) [0, 1, 2] >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 2, 4) [2] >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 3) [3, 4, 5] >>> _trimchunk(revlog, [0, 1, 2, 3, 4, 5, 6], 3, 5) [3, 4] Discontiguous cases: >>> _trimchunk(revlog, [1, 3, 5, 6], 0) [1, 3, 5] >>> _trimchunk(revlog, [1, 3, 5, 6], 0, 2) [1] >>> _trimchunk(revlog, [1, 3, 5, 6], 1, 3) [3, 5] >>> _trimchunk(revlog, [1, 3, 5, 6], 1) [3, 5] """ length = revlog.length if endidx is None: endidx = len(revs) # If we have a non-emtpy delta candidate, there are nothing to trim if revs[endidx - 1] < len(revlog): # Trim empty revs at the end, except the very first revision of a chain while (endidx > 1 and endidx > startidx and length(revs[endidx - 1]) == 0): endidx -= 1 return revs[startidx:endidx] def segmentspan(revlog, revs, deltainfo=None): """Get the byte span of a segment of revisions revs is a sorted array of revision numbers >>> revlog = _testrevlog([ ... 5, #0 ... 10, #1 ... 12, #2 ... 12, #3 (empty) ... 17, #4 ... ]) >>> segmentspan(revlog, [0, 1, 2, 3, 4]) 17 >>> segmentspan(revlog, [0, 4]) 17 >>> segmentspan(revlog, [3, 4]) 5 >>> segmentspan(revlog, [1, 2, 3,]) 7 >>> segmentspan(revlog, [1, 3]) 7 """ if not revs: return 0 if deltainfo is not None and len(revlog) <= revs[-1]: if len(revs) == 1: return deltainfo.deltalen offset = revlog.end(len(revlog) - 1) end = deltainfo.deltalen + offset else: end = revlog.end(revs[-1]) return end - revlog.start(revs[0]) def _textfromdelta(fh, revlog, baserev, delta, p1, p2, flags, expectednode): """build full text from a (base, delta) pair and other metadata""" # special case deltas which replace entire base; no need to decode # base revision. this neatly avoids censored bases, which throw when # they're decoded. hlen = struct.calcsize(">lll") if delta[:hlen] == mdiff.replacediffheader(revlog.rawsize(baserev), len(delta) - hlen): fulltext = delta[hlen:] else: # deltabase is rawtext before changed by flag processors, which is # equivalent to non-raw text basetext = revlog.revision(baserev, _df=fh, raw=False) fulltext = mdiff.patch(basetext, delta) try: res = revlog._processflags(fulltext, flags, 'read', raw=True) fulltext, validatehash = res if validatehash: revlog.checkhash(fulltext, expectednode, p1=p1, p2=p2) if flags & REVIDX_ISCENSORED: raise RevlogError(_('node %s is not censored') % expectednode) except CensoredNodeError: # must pass the censored index flag to add censored revisions if not flags & REVIDX_ISCENSORED: raise return fulltext @attr.s(slots=True, frozen=True) class _deltainfo(object): distance = attr.ib() deltalen = attr.ib() data = attr.ib() base = attr.ib() chainbase = attr.ib() chainlen = attr.ib() compresseddeltalen = attr.ib() snapshotdepth = attr.ib() def isgooddeltainfo(revlog, deltainfo, revinfo): """Returns True if the given delta is good. Good means that it is within the disk span, disk size, and chain length bounds that we know to be performant.""" if deltainfo is None: return False # - 'deltainfo.distance' is the distance from the base revision -- # bounding it limits the amount of I/O we need to do. # - 'deltainfo.compresseddeltalen' is the sum of the total size of # deltas we need to apply -- bounding it limits the amount of CPU # we consume. if revlog._sparserevlog: # As sparse-read will be used, we can consider that the distance, # instead of being the span of the whole chunk, # is the span of the largest read chunk base = deltainfo.base if base != nullrev: deltachain = revlog._deltachain(base)[0] else: deltachain = [] # search for the first non-snapshot revision for idx, r in enumerate(deltachain): if not revlog.issnapshot(r): break deltachain = deltachain[idx:] chunks = slicechunk(revlog, deltachain, deltainfo) all_span = [segmentspan(revlog, revs, deltainfo) for revs in chunks] distance = max(all_span) else: distance = deltainfo.distance textlen = revinfo.textlen defaultmax = textlen * 4 maxdist = revlog._maxdeltachainspan if not maxdist: maxdist = distance # ensure the conditional pass maxdist = max(maxdist, defaultmax) if revlog._sparserevlog and maxdist < revlog._srmingapsize: # In multiple place, we are ignoring irrelevant data range below a # certain size. Be also apply this tradeoff here and relax span # constraint for small enought content. maxdist = revlog._srmingapsize # Bad delta from read span: # # If the span of data read is larger than the maximum allowed. if maxdist < distance: return False # Bad delta from new delta size: # # If the delta size is larger than the target text, storing the # delta will be inefficient. if textlen < deltainfo.deltalen: return False # Bad delta from cumulated payload size: # # If the sum of delta get larger than K * target text length. if textlen * LIMIT_DELTA2TEXT < deltainfo.compresseddeltalen: return False # Bad delta from chain length: # # If the number of delta in the chain gets too high. if (revlog._maxchainlen and revlog._maxchainlen < deltainfo.chainlen): return False # bad delta from intermediate snapshot size limit # # If an intermediate snapshot size is higher than the limit. The # limit exist to prevent endless chain of intermediate delta to be # created. if (deltainfo.snapshotdepth is not None and (textlen >> deltainfo.snapshotdepth) < deltainfo.deltalen): return False # bad delta if new intermediate snapshot is larger than the previous # snapshot if (deltainfo.snapshotdepth and revlog.length(deltainfo.base) < deltainfo.deltalen): return False return True def _candidategroups(revlog, textlen, p1, p2, cachedelta): """Provides group of revision to be tested as delta base This top level function focus on emitting groups with unique and worthwhile content. See _raw_candidate_groups for details about the group order. """ # should we try to build a delta? if not (len(revlog) and revlog._storedeltachains): return deltalength = revlog.length deltaparent = revlog.deltaparent deltas_limit = textlen * LIMIT_DELTA2TEXT tested = set([nullrev]) for temptative in _rawgroups(revlog, p1, p2, cachedelta): group = [] for rev in temptative: # skip over empty delta (no need to include them in a chain) while not (rev == nullrev or rev in tested or deltalength(rev)): rev = deltaparent(rev) tested.add(rev) # filter out revision we tested already if rev in tested: continue tested.add(rev) # filter out delta base that will never produce good delta if deltas_limit < revlog.length(rev): continue # no need to try a delta against nullrev, this will be done as a # last resort. if rev == nullrev: continue # no delta for rawtext-changing revs (see "candelta" for why) if revlog.flags(rev) & REVIDX_RAWTEXT_CHANGING_FLAGS: continue group.append(rev) if group: yield tuple(group) def _rawgroups(revlog, p1, p2, cachedelta): """Provides group of revision to be tested as delta base This lower level function focus on emitting delta theorically interresting without looking it any practical details. The group order aims at providing fast or small candidates first. """ gdelta = revlog._generaldelta curr = len(revlog) prev = curr - 1 # This condition is true most of the time when processing # changegroup data into a generaldelta repo. The only time it # isn't true is if this is the first revision in a delta chain # or if ``format.generaldelta=true`` disabled ``lazydeltabase``. if cachedelta and gdelta and revlog._lazydeltabase: # Assume what we received from the server is a good choice # build delta will reuse the cache yield (cachedelta[0],) if gdelta: # exclude already lazy tested base if any parents = [p for p in (p1, p2) if p != nullrev] if not revlog._deltabothparents and len(parents) == 2: parents.sort() # To minimize the chance of having to build a fulltext, # pick first whichever parent is closest to us (max rev) yield (parents[1],) # then the other one (min rev) if the first did not fit yield (parents[0],) elif len(parents) > 0: # Test all parents (1 or 2), and keep the best candidate yield parents # other approach failed try against prev to hopefully save us a # fulltext. yield (prev,) class deltacomputer(object): def __init__(self, revlog): self.revlog = revlog def buildtext(self, revinfo, fh): """Builds a fulltext version of a revision revinfo: _revisioninfo instance that contains all needed info fh: file handle to either the .i or the .d revlog file, depending on whether it is inlined or not """ btext = revinfo.btext if btext[0] is not None: return btext[0] revlog = self.revlog cachedelta = revinfo.cachedelta baserev = cachedelta[0] delta = cachedelta[1] fulltext = btext[0] = _textfromdelta(fh, revlog, baserev, delta, revinfo.p1, revinfo.p2, revinfo.flags, revinfo.node) return fulltext def _builddeltadiff(self, base, revinfo, fh): revlog = self.revlog t = self.buildtext(revinfo, fh) if revlog.iscensored(base): # deltas based on a censored revision must replace the # full content in one patch, so delta works everywhere header = mdiff.replacediffheader(revlog.rawsize(base), len(t)) delta = header + t else: ptext = revlog.revision(base, _df=fh, raw=True) delta = mdiff.textdiff(ptext, t) return delta def _builddeltainfo(self, revinfo, base, fh): # can we use the cached delta? if revinfo.cachedelta and revinfo.cachedelta[0] == base: delta = revinfo.cachedelta[1] else: delta = self._builddeltadiff(base, revinfo, fh) revlog = self.revlog header, data = revlog.compress(delta) deltalen = len(header) + len(data) chainbase = revlog.chainbase(base) offset = revlog.end(len(revlog) - 1) dist = deltalen + offset - revlog.start(chainbase) if revlog._generaldelta: deltabase = base else: deltabase = chainbase chainlen, compresseddeltalen = revlog._chaininfo(base) chainlen += 1 compresseddeltalen += deltalen revlog = self.revlog snapshotdepth = None if deltabase == nullrev: snapshotdepth = 0 elif revlog._sparserevlog and revlog.issnapshot(deltabase): # A delta chain should always be one full snapshot, # zero or more semi-snapshots, and zero or more deltas p1, p2 = revlog.rev(revinfo.p1), revlog.rev(revinfo.p2) if deltabase not in (p1, p2) and revlog.issnapshot(deltabase): snapshotdepth = len(revlog._deltachain(deltabase)[0]) return _deltainfo(dist, deltalen, (header, data), deltabase, chainbase, chainlen, compresseddeltalen, snapshotdepth) def _fullsnapshotinfo(self, fh, revinfo): curr = len(self.revlog) rawtext = self.buildtext(revinfo, fh) data = self.revlog.compress(rawtext) compresseddeltalen = deltalen = dist = len(data[1]) + len(data[0]) deltabase = chainbase = curr snapshotdepth = 0 chainlen = 1 return _deltainfo(dist, deltalen, data, deltabase, chainbase, chainlen, compresseddeltalen, snapshotdepth) def finddeltainfo(self, revinfo, fh): """Find an acceptable delta against a candidate revision revinfo: information about the revision (instance of _revisioninfo) fh: file handle to either the .i or the .d revlog file, depending on whether it is inlined or not Returns the first acceptable candidate revision, as ordered by _candidategroups If no suitable deltabase is found, we return delta info for a full snapshot. """ if not revinfo.textlen: return self._fullsnapshotinfo(fh, revinfo) # no delta for flag processor revision (see "candelta" for why) # not calling candelta since only one revision needs test, also to # avoid overhead fetching flags again. if revinfo.flags & REVIDX_RAWTEXT_CHANGING_FLAGS: return self._fullsnapshotinfo(fh, revinfo) cachedelta = revinfo.cachedelta p1 = revinfo.p1 p2 = revinfo.p2 revlog = self.revlog deltainfo = None p1r, p2r = revlog.rev(p1), revlog.rev(p2) groups = _candidategroups(self.revlog, revinfo.textlen, p1r, p2r, cachedelta) for candidaterevs in groups: nominateddeltas = [] for candidaterev in candidaterevs: candidatedelta = self._builddeltainfo(revinfo, candidaterev, fh) if isgooddeltainfo(self.revlog, candidatedelta, revinfo): nominateddeltas.append(candidatedelta) if nominateddeltas: deltainfo = min(nominateddeltas, key=lambda x: x.deltalen) break if deltainfo is None: deltainfo = self._fullsnapshotinfo(fh, revinfo) return deltainfo