upstream/mercurial-mirror Files · mercurial/peer.py

strip: make query to get new bookmark target cheaper...

strip: make query to get new bookmark target cheaper The current query to get the new bookmark target for stripped revisions involves multiple walks up the DAG, and is really expensive, taking over 2.5 seconds on a repository with over 400,000 changesets even if just one changeset is being stripped. A slightly simplified version of the current query is max(heads(::<tostrip> - <tostrip>)) We make two observations here. 1. For any set s, max(heads(s)) == max(s). That is because revision numbers define a topological order, so that the element with the highest revision number in s will not have any children in s. 2. For any set s, max(::s - s) == max(parents(s) - s). In other words, the ancestor of s with the highest revision number not in s is a parent of one of the revs in s. Why? Because if it were an ancestor but not a parent of s, it would have a descendant that would be a parent of s. This descendant would have a higher revision number, leading to a contradiction. Combining these two observations, we rewrite the revset query as max(parents(<tostrip>) - <tostrip>) The time complexity is now linear in the number of changesets being stripped. For the above repository, the query now takes 0.1 seconds when one changeset is stripped. This speeds up operations that use repair.strip, like the rebase and strip commands.

Simon Heimberg - - Load All Authors

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      # peer.py - repository base classes for mercurial

      #

      # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>

      # Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com>

      #

      # This software may be used and distributed according to the terms of the

      # GNU General Public License version 2 or any later version.

      from i18n import _

      import error

      class peerrepository(object):

          def capable(self, name):

              '''tell whether repo supports named capability.

              return False if not supported.

              if boolean capability, return True.

              if string capability, return string.'''

              caps = self._capabilities()

              if name in caps:

                  return True

              name_eq = name + '='

              for cap in caps:

                  if cap.startswith(name_eq):

                      return cap[len(name_eq):]

              return False

          def requirecap(self, name, purpose):

              '''raise an exception if the given capability is not present'''

              if not self.capable(name):

                  raise error.CapabilityError(

                      _('cannot %s; remote repository does not '

                        'support the %r capability') % (purpose, name))

          def local(self):

              '''return peer as a localrepo, or None'''

              return None

          def peer(self):

              return self

          def canpush(self):

              return True

          def close(self):

              pass

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				# peer.py - repository base classes for mercurial
				#
				# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
				# Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com>
				#
				# This software may be used and distributed according to the terms of the
				# GNU General Public License version 2 or any later version.

				from i18n import _
				import error

				class peerrepository(object):

				def capable(self, name):
				'''tell whether repo supports named capability.
				return False if not supported.
				if boolean capability, return True.
				if string capability, return string.'''
				caps = self._capabilities()
				if name in caps:
				return True
				name_eq = name + '='
				for cap in caps:
				if cap.startswith(name_eq):
				return cap[len(name_eq):]
				return False

				def requirecap(self, name, purpose):
				'''raise an exception if the given capability is not present'''
				if not self.capable(name):
				raise error.CapabilityError(
				_('cannot %s; remote repository does not '
				'support the %r capability') % (purpose, name))

				def local(self):
				'''return peer as a localrepo, or None'''
				return None

				def peer(self):
				return self

				def canpush(self):
				return True

				def close(self):
				pass