comparison mercurial/revset.py @ 33080:a53bfc2845f2

revset: add depth limit to descendants() (issue5374)

This is naive implementation using two-pass scanning. Tracking descendants
isn't an easy problem if both start and stop depths are specified. It's
impractical to remember all possible depths of each node while scanning from
roots to descendants because the number of depths explodes. Instead, we could
cache (min, max) depths as a good approximation and track ancestors back when
needed, but that's likely to have off-by-one bug.

Since this implementation appears not significantly slower, and is quite
straightforward, I think it's good enough for practical use cases. The time
and space complexity is O(n) ish.

  revisions:
  0) 1-pass scanning with (min, max)-depth cache (worst-case quadratic)
  1) 2-pass scanning (this version)

  repository:
  mozilla-central

  # descendants(0) (for reference)
  *) 0.430353

  # descendants(0, depth=1000)
  0) 0.264889
  1) 0.398289

  # descendants(limit(tip:0, 1, offset=10000), depth=1000)
  0) 0.025478
  1) 0.029099

  # descendants(0, depth=2000, startdepth=1000)
  0) painfully slow (due to quadratic backtracking of ancestors)
  1) 1.531138

33079:550c390cd9b2

    kind, pattern, matcher = _substringmatcher(ds, casesensitive=False)

    return subset.filter(lambda r: matcher(repo[r].description()),
                         condrepr=('<desc %r>', ds))

def _descendants(repo, subset, x, followfirst=False):
    roots = getset(repo, fullreposet(repo), x)
    if not roots:
        return baseset()
    s = dagop.revdescendants(repo, roots, followfirst)
    return subset & s

@predicate('descendants(set)', safe=True)
def descendants(repo, subset, x):
    """Changesets which are descendants of changesets in set, including the
    given changesets themselves.
    """
    args = getargsdict(x, 'descendants', 'set')
    if 'set' not in args:
        # i18n: "descendants" is a keyword
        raise error.ParseError(_('descendants takes at least 1 argument'))
    return _descendants(repo, subset, args['set'])

@predicate('_firstdescendants', safe=True)
def _firstdescendants(repo, subset, x):
    # ``_firstdescendants(set)``
    # Like ``descendants(set)`` but follows only the first parents.

33080:a53bfc2845f2

    kind, pattern, matcher = _substringmatcher(ds, casesensitive=False)

    return subset.filter(lambda r: matcher(repo[r].description()),
                         condrepr=('<desc %r>', ds))

def _descendants(repo, subset, x, followfirst=False, startdepth=None,
                 stopdepth=None):
    roots = getset(repo, fullreposet(repo), x)
    if not roots:
        return baseset()
    s = dagop.revdescendants(repo, roots, followfirst, startdepth, stopdepth)
    return subset & s

@predicate('descendants(set[, depth])', safe=True)
def descendants(repo, subset, x):
    """Changesets which are descendants of changesets in set, including the
    given changesets themselves.

    If depth is specified, the result only includes changesets up to
    the specified generation.
    """
    # startdepth is for internal use only until we can decide the UI
    args = getargsdict(x, 'descendants', 'set depth startdepth')
    if 'set' not in args:
        # i18n: "descendants" is a keyword
        raise error.ParseError(_('descendants takes at least 1 argument'))
    startdepth = stopdepth = None
    if 'startdepth' in args:
        n = getinteger(args['startdepth'],
                       "descendants expects an integer startdepth")
        if n < 0:
            raise error.ParseError("negative startdepth")
        startdepth = n
    if 'depth' in args:
        # i18n: "descendants" is a keyword
        n = getinteger(args['depth'], _("descendants expects an integer depth"))
        if n < 0:
            raise error.ParseError(_("negative depth"))
        stopdepth = n + 1
    return _descendants(repo, subset, args['set'],
                        startdepth=startdepth, stopdepth=stopdepth)

@predicate('_firstdescendants', safe=True)
def _firstdescendants(repo, subset, x):
    # ``_firstdescendants(set)``
    # Like ``descendants(set)`` but follows only the first parents.