contrib/shrink-revlog.py

#!/usr/bin/env python

"""\
Reorder a revlog (by default the the manifest file in the current
repository) to save space.  Specifically, this topologically sorts the
revisions in the revlog so that revisions on the same branch are adjacent
as much as possible.  This is a workaround for the fact that Mercurial
computes deltas relative to the previous revision rather than relative to a
parent revision.  This is *not* safe to run on a changelog.
"""

# Originally written by Benoit Boissinot <benoit.boissinot at ens-lyon.org>
# as a patch to rewrite-log.  Cleaned up, refactored, documented, and
# renamed by Greg Ward <greg at gerg.ca>.

# XXX would be nice to have a way to verify the repository after shrinking,
# e.g. by comparing "before" and "after" states of random changesets
# (maybe: export before, shrink, export after, diff).

import sys, os, tempfile
import optparse
from mercurial import ui as ui_, hg, revlog, transaction, node, util
from mercurial import changegroup

def toposort(ui, rl):

    children = {}
    root = []
    # build children and roots
    ui.write('reading %d revs ' % len(rl))
    try:
        for i in rl:
            children[i] = []
            parents = [p for p in rl.parentrevs(i) if p != node.nullrev]
            # in case of duplicate parents
            if len(parents) == 2 and parents[0] == parents[1]:
                del parents[1]
            for p in parents:
                assert p in children
                children[p].append(i)

            if len(parents) == 0:
                root.append(i)

            if i % 1000 == 0:
                ui.write('.')
    finally:
        ui.write('\n')

    # XXX this is a reimplementation of the 'branchsort' topo sort
    # algorithm in hgext.convert.convcmd... would be nice not to duplicate
    # the algorithm
    ui.write('sorting ...')
    visit = root
    ret = []
    while visit:
        i = visit.pop(0)
        ret.append(i)
        if i not in children:
            # This only happens if some node's p1 == p2, which can
            # happen in the manifest in certain circumstances.
            continue
        next = []
        for c in children.pop(i):
            parents_unseen = [p for p in rl.parentrevs(c)
                              if p != node.nullrev and p in children]
            if len(parents_unseen) == 0:
                next.append(c)
        visit = next + visit
    ui.write('\n')
    return ret

def writerevs(ui, r1, r2, order, tr):

    ui.write('writing %d revs ' % len(order))
    count = [0]
    def progress(*args):
        if count[0] % 1000 == 0:
            ui.write('.')
        count[0] += 1

    order = [r1.node(r) for r in order]

    # this is a bit ugly, but it works
    lookup = lambda x: "%020d" % r1.linkrev(r1.rev(x))
    unlookup = lambda x: int(x, 10)

    try:
        group = util.chunkbuffer(r1.group(order, lookup, progress))
        chunkiter = changegroup.chunkiter(group)
        r2.addgroup(chunkiter, unlookup, tr)
    finally:
        ui.write('\n')

def report(ui, olddatafn, newdatafn):
    oldsize = float(os.stat(olddatafn).st_size)
    newsize = float(os.stat(newdatafn).st_size)

    # argh: have to pass an int to %d, because a float >= 2^32
    # blows up under Python 2.5 or earlier
    ui.write('old file size: %12d bytes (%6.1f MiB)\n'
             % (int(oldsize), oldsize/1024/1024))
    ui.write('new file size: %12d bytes (%6.1f MiB)\n'
             % (int(newsize), newsize/1024/1024))

    shrink_percent = (oldsize - newsize) / oldsize * 100
    shrink_factor = oldsize / newsize
    ui.write('shrinkage: %.1f%% (%.1fx)\n' % (shrink_percent, shrink_factor))

def main():

    # Unbuffer stdout for nice progress output.
    sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)

    parser = optparse.OptionParser(description=__doc__)
    parser.add_option('-R', '--repository',
                      default=os.path.curdir,
                      metavar='REPO',
                      help='repository root directory [default: current dir]')
    parser.add_option('--revlog',
                      metavar='FILE',
                      help='shrink FILE [default: REPO/hg/store/00manifest.i]')
    (options, args) = parser.parse_args()
    if args:
        raise util.Abort('too many arguments')

    # Open the specified repository.
    ui = ui_.ui()
    repo = hg.repository(ui, options.repository)
    if not repo.local():
        raise util.Abort('not a local repository: %s' % options.repository)

    if options.revlog is None:
        indexfn = repo.sjoin('00manifest.i')
    else:
        if not options.revlog.endswith('.i'):
            raise util.Abort('--revlog option must specify the revlog index '
                             'file (*.i), not %s' % options.revlog)

        indexfn = os.path.realpath(options.revlog)
        store = repo.sjoin('')
        if not indexfn.startswith(store):
            raise util.Abort('--revlog option must specify a revlog in %s, '
                             'not %s' % (store, indexfn))

    datafn = indexfn[:-2] + '.d'
    if not os.path.exists(indexfn):
        raise util.Abort('no such file: %s' % indexfn)
    if '00changelog' in indexfn:
        raise util.Abort('shrinking the changelog will corrupt your repository')
    if not os.path.exists(datafn):
        # This is just a lazy shortcut because I can't be bothered to
        # handle all the special cases that entail from no .d file.
        raise util.Abort('%s does not exist: revlog not big enough '
                         'to be worth shrinking' % datafn)

    oldindexfn = indexfn + '.old'
    olddatafn = datafn + '.old'
    if os.path.exists(oldindexfn) or os.path.exists(olddatafn):
        raise util.Abort('one or both of\n'
                         '  %s\n'
                         '  %s\n'
                         'exists from a previous run; please clean up before '
                         'running again' % (oldindexfn, olddatafn))

    ui.write('shrinking %s\n' % indexfn)
    prefix = os.path.basename(indexfn)[:-1]
    (tmpfd, tmpindexfn) = tempfile.mkstemp(dir=os.path.dirname(indexfn),
                                           prefix=prefix,
                                           suffix='.i')
    tmpdatafn = tmpindexfn[:-2] + '.d'
    os.close(tmpfd)

    r1 = revlog.revlog(util.opener(os.getcwd(), audit=False), indexfn)
    r2 = revlog.revlog(util.opener(os.getcwd(), audit=False), tmpindexfn)

    # Don't use repo.transaction(), because then things get hairy with
    # paths: some need to be relative to .hg, and some need to be
    # absolute.  Doing it this way keeps things simple: everything is an
    # absolute path.
    lock = repo.lock(wait=False)
    tr = transaction.transaction(sys.stderr.write,
                                 open,
                                 repo.sjoin('journal'))

    try:
        try:
            order = toposort(ui, r1)
            writerevs(ui, r1, r2, order, tr)
            report(ui, datafn, tmpdatafn)
            tr.close()
        except:
            # Abort transaction first, so we truncate the files before
            # deleting them.
            tr.abort()
            if os.path.exists(tmpindexfn):
                os.unlink(tmpindexfn)
            if os.path.exists(tmpdatafn):
                os.unlink(tmpdatafn)
            raise
    finally:
        lock.release()

    os.link(indexfn, oldindexfn)
    os.link(datafn, olddatafn)
    os.rename(tmpindexfn, indexfn)
    os.rename(tmpdatafn, datafn)
    ui.write('note: old revlog saved in:\n'
          '  %s\n'
          '  %s\n'
          '(You can delete those files when you are satisfied that your\n'
          'repository is still sane.  '
          'Running \'hg verify\' is strongly recommended.)\n'
          % (oldindexfn, olddatafn))

try:
    main()
except util.Abort, inst:
    print inst.args[0]
except KeyboardInterrupt:
    sys.exit("interrupted")