[Bug 4572] New: lazymanifest makes hg revert --all -r .^ takes 60+s on large repos

[mercurial-bugs at selenic.com]

http://bz.selenic.com/show_bug.cgi?id=4572

          Priority: normal
            Bug ID: 4572
                CC: durin42 at gmail.com, martinvonz at google.com,
                    mercurial-devel at selenic.com
          Assignee: bugzilla at selenic.com
           Summary: lazymanifest makes hg revert --all -r .^ takes 60+s on
                    large repos
          Severity: bug
    Classification: Unclassified
                OS: Mac OS
          Reporter: durham at fb.com
          Hardware: PC
            Status: UNCONFIRMED
           Version: default branch
         Component: Mercurial
           Product: Mercurial

With the the new lazymanifest bits, 'hg revert -r .^ --all' takes 60s. This is
caused by manifestdict.intersectfiles being implemented as:

    def intersectfiles(self, files):
        ret = manifestdict()
        lm = self._lm
        for fn in files:
            if fn in lm:
                ret._lm[fn] = self._lm[fn]
        return ret

where len(files) is huge and every 'fn in files' check takes O(log len(lm)).  A
temporary solution might be to add a set here if len(files) > 1000 or so.  The
right fix is to probably move intersectfiles into c code and do the look ups
intelligently across the lazy manifest.

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