Mercurial > hg
view mercurial/metadata.py @ 45059:79f6f9fa18c1
documentation: add some internals documentation about bid merge
This is an important algorithm that was only documented on the wiki so far.
Some update to the algorithm (and associated doc) is to expected in the future
since the bid merge algorithm is bug-ridden when it comes to file deletion comes
to play.
Differential Revision: https://phab.mercurial-scm.org/D8711
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
---|---|
date | Mon, 22 Jun 2020 13:32:20 +0200 |
parents | 25512a65cefd |
children | aea6a812f7cb |
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# metadata.py -- code related to various metadata computation and access. # # Copyright 2019 Google, Inc <martinvonz@google.com> # Copyright 2020 Pierre-Yves David <pierre-yves.david@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, print_function import multiprocessing from . import ( error, node, pycompat, util, ) from .revlogutils import ( flagutil as sidedataflag, sidedata as sidedatamod, ) def computechangesetfilesadded(ctx): """return the list of files added in a changeset """ added = [] for f in ctx.files(): if not any(f in p for p in ctx.parents()): added.append(f) return added def get_removal_filter(ctx, x=None): """return a function to detect files "wrongly" detected as `removed` When a file is removed relative to p1 in a merge, this function determines whether the absence is due to a deletion from a parent, or whether the merge commit itself deletes the file. We decide this by doing a simplified three way merge of the manifest entry for the file. There are two ways we decide the merge itself didn't delete a file: - neither parent (nor the merge) contain the file - exactly one parent contains the file, and that parent has the same filelog entry as the merge ancestor (or all of them if there two). In other words, that parent left the file unchanged while the other one deleted it. One way to think about this is that deleting a file is similar to emptying it, so the list of changed files should be similar either way. The computation described above is not done directly in _filecommit when creating the list of changed files, however it does something very similar by comparing filelog nodes. """ if x is not None: p1, p2, m1, m2 = x else: p1 = ctx.p1() p2 = ctx.p2() m1 = p1.manifest() m2 = p2.manifest() @util.cachefunc def mas(): p1n = p1.node() p2n = p2.node() cahs = ctx.repo().changelog.commonancestorsheads(p1n, p2n) if not cahs: cahs = [node.nullrev] return [ctx.repo()[r].manifest() for r in cahs] def deletionfromparent(f): if f in m1: return f not in m2 and all( f in ma and ma.find(f) == m1.find(f) for ma in mas() ) elif f in m2: return all(f in ma and ma.find(f) == m2.find(f) for ma in mas()) else: return True return deletionfromparent def computechangesetfilesremoved(ctx): """return the list of files removed in a changeset """ removed = [] for f in ctx.files(): if f not in ctx: removed.append(f) if removed: rf = get_removal_filter(ctx) removed = [r for r in removed if not rf(r)] return removed def computechangesetcopies(ctx): """return the copies data for a changeset The copies data are returned as a pair of dictionnary (p1copies, p2copies). Each dictionnary are in the form: `{newname: oldname}` """ p1copies = {} p2copies = {} p1 = ctx.p1() p2 = ctx.p2() narrowmatch = ctx._repo.narrowmatch() for dst in ctx.files(): if not narrowmatch(dst) or dst not in ctx: continue copied = ctx[dst].renamed() if not copied: continue src, srcnode = copied if src in p1 and p1[src].filenode() == srcnode: p1copies[dst] = src elif src in p2 and p2[src].filenode() == srcnode: p2copies[dst] = src return p1copies, p2copies def encodecopies(files, copies): items = [] for i, dst in enumerate(files): if dst in copies: items.append(b'%d\0%s' % (i, copies[dst])) if len(items) != len(copies): raise error.ProgrammingError( b'some copy targets missing from file list' ) return b"\n".join(items) def decodecopies(files, data): try: copies = {} if not data: return copies for l in data.split(b'\n'): strindex, src = l.split(b'\0') i = int(strindex) dst = files[i] copies[dst] = src return copies except (ValueError, IndexError): # Perhaps someone had chosen the same key name (e.g. "p1copies") and # used different syntax for the value. return None def encodefileindices(files, subset): subset = set(subset) indices = [] for i, f in enumerate(files): if f in subset: indices.append(b'%d' % i) return b'\n'.join(indices) def decodefileindices(files, data): try: subset = [] if not data: return subset for strindex in data.split(b'\n'): i = int(strindex) if i < 0 or i >= len(files): return None subset.append(files[i]) return subset except (ValueError, IndexError): # Perhaps someone had chosen the same key name (e.g. "added") and # used different syntax for the value. return None def _getsidedata(srcrepo, rev): ctx = srcrepo[rev] filescopies = computechangesetcopies(ctx) filesadded = computechangesetfilesadded(ctx) filesremoved = computechangesetfilesremoved(ctx) sidedata = {} if any([filescopies, filesadded, filesremoved]): sortedfiles = sorted(ctx.files()) p1copies, p2copies = filescopies p1copies = encodecopies(sortedfiles, p1copies) p2copies = encodecopies(sortedfiles, p2copies) filesadded = encodefileindices(sortedfiles, filesadded) filesremoved = encodefileindices(sortedfiles, filesremoved) if p1copies: sidedata[sidedatamod.SD_P1COPIES] = p1copies if p2copies: sidedata[sidedatamod.SD_P2COPIES] = p2copies if filesadded: sidedata[sidedatamod.SD_FILESADDED] = filesadded if filesremoved: sidedata[sidedatamod.SD_FILESREMOVED] = filesremoved return sidedata def getsidedataadder(srcrepo, destrepo): use_w = srcrepo.ui.configbool(b'experimental', b'worker.repository-upgrade') if pycompat.iswindows or not use_w: return _get_simple_sidedata_adder(srcrepo, destrepo) else: return _get_worker_sidedata_adder(srcrepo, destrepo) def _sidedata_worker(srcrepo, revs_queue, sidedata_queue, tokens): """The function used by worker precomputing sidedata It read an input queue containing revision numbers It write in an output queue containing (rev, <sidedata-map>) The `None` input value is used as a stop signal. The `tokens` semaphore is user to avoid having too many unprocessed entries. The workers needs to acquire one token before fetching a task. They will be released by the consumer of the produced data. """ tokens.acquire() rev = revs_queue.get() while rev is not None: data = _getsidedata(srcrepo, rev) sidedata_queue.put((rev, data)) tokens.acquire() rev = revs_queue.get() # processing of `None` is completed, release the token. tokens.release() BUFF_PER_WORKER = 50 def _get_worker_sidedata_adder(srcrepo, destrepo): """The parallel version of the sidedata computation This code spawn a pool of worker that precompute a buffer of sidedata before we actually need them""" # avoid circular import copies -> scmutil -> worker -> copies from . import worker nbworkers = worker._numworkers(srcrepo.ui) tokens = multiprocessing.BoundedSemaphore(nbworkers * BUFF_PER_WORKER) revsq = multiprocessing.Queue() sidedataq = multiprocessing.Queue() assert srcrepo.filtername is None # queue all tasks beforehand, revision numbers are small and it make # synchronisation simpler # # Since the computation for each node can be quite expensive, the overhead # of using a single queue is not revelant. In practice, most computation # are fast but some are very expensive and dominate all the other smaller # cost. for r in srcrepo.changelog.revs(): revsq.put(r) # queue the "no more tasks" markers for i in range(nbworkers): revsq.put(None) allworkers = [] for i in range(nbworkers): args = (srcrepo, revsq, sidedataq, tokens) w = multiprocessing.Process(target=_sidedata_worker, args=args) allworkers.append(w) w.start() # dictionnary to store results for revision higher than we one we are # looking for. For example, if we need the sidedatamap for 42, and 43 is # received, when shelve 43 for later use. staging = {} def sidedata_companion(revlog, rev): sidedata = {} if util.safehasattr(revlog, b'filteredrevs'): # this is a changelog # Is the data previously shelved ? sidedata = staging.pop(rev, None) if sidedata is None: # look at the queued result until we find the one we are lookig # for (shelve the other ones) r, sidedata = sidedataq.get() while r != rev: staging[r] = sidedata r, sidedata = sidedataq.get() tokens.release() return False, (), sidedata return sidedata_companion def _get_simple_sidedata_adder(srcrepo, destrepo): """The simple version of the sidedata computation It just compute it in the same thread on request""" def sidedatacompanion(revlog, rev): sidedata = {} if util.safehasattr(revlog, 'filteredrevs'): # this is a changelog sidedata = _getsidedata(srcrepo, rev) return False, (), sidedata return sidedatacompanion def getsidedataremover(srcrepo, destrepo): def sidedatacompanion(revlog, rev): f = () if util.safehasattr(revlog, 'filteredrevs'): # this is a changelog if revlog.flags(rev) & sidedataflag.REVIDX_SIDEDATA: f = ( sidedatamod.SD_P1COPIES, sidedatamod.SD_P2COPIES, sidedatamod.SD_FILESADDED, sidedatamod.SD_FILESREMOVED, ) return False, f, {} return sidedatacompanion