view mercurial/error.py @ 29304:5e32852fa4bd

revset: make filteredset.__nonzero__ respect the order of the filteredset

This fix allows __nonzero__ to respect the direction of iteration of the
whole filteredset. Here's the case when it matters. Imagine that we have a
very large repository and we want to execute a command like:

    $ hg log --rev '(tip:0) and user(ikostia)' --limit 1

(we want to get the latest commit by me).

Mercurial will evaluate a filteredset lazy data structure, an
instance of the filteredset class, which will know that it has to iterate
in a descending order (isdescending() will return True if called). This
means that when some code iterates over the instance of this filteredset,
the 'and user(ikostia)' condition will be first checked on the latest
revision, then on the second latest and so on, allowing Mercurial to
print matches as it founds them. However, cmdutil.getgraphlogrevs
contains the following code:

    revs = _logrevs(repo, opts)
    if not revs:
        return revset.baseset(), None, None

The "not revs" expression is evaluated by calling filteredset.__nonzero__,
which in its current implementation will try to iterate the filteredset
in ascending order until it finds a revision that matches the 'and user(..'
condition. If the condition is only true on late revisions, a lot of
useless iterations will be done. These iterations could be avoided if
__nonzero__ followed the order of the filteredset, which in my opinion
is a sensible thing to do here.

The problem gets even worse when instead of 'user(ikostia)' some more
expensive check is performed, like grepping the commit diff.


I tested this fix on a very large repo where tip is my commit and my very
first commit comes fairly late in the revision history. Results of timing
of the above command on that very large repo.

-with my fix:
real    0m1.795s
user    0m1.657s
sys     0m0.135s

-without my fix:
real    1m29.245s
user    1m28.223s
sys     0m0.929s

I understand that this is a very specific kind of problem that presents
itself very rarely, only on very big repositories and with expensive
checks and so on. But I don't see any disadvantages to this kind of fix
either.

# error.py - Mercurial exceptions
#
# Copyright 2005-2008 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""Mercurial exceptions.

This allows us to catch exceptions at higher levels without forcing
imports.
"""

from __future__ import absolute_import

# Do not import anything here, please

class HintException(Exception):
    def __init__(self, *args, **kw):
        Exception.__init__(self, *args)
        self.hint = kw.get('hint')

class RevlogError(HintException):
    pass

class FilteredIndexError(IndexError):
    pass

class LookupError(RevlogError, KeyError):
    def __init__(self, name, index, message):
        self.name = name
        self.index = index
        # this can't be called 'message' because at least some installs of
        # Python 2.6+ complain about the 'message' property being deprecated
        self.lookupmessage = message
        if isinstance(name, str) and len(name) == 20:
            from .node import short
            name = short(name)
        RevlogError.__init__(self, '%s@%s: %s' % (index, name, message))

    def __str__(self):
        return RevlogError.__str__(self)

class FilteredLookupError(LookupError):
    pass

class ManifestLookupError(LookupError):
    pass

class CommandError(Exception):
    """Exception raised on errors in parsing the command line."""

class InterventionRequired(HintException):
    """Exception raised when a command requires human intervention."""

class Abort(HintException):
    """Raised if a command needs to print an error and exit."""

class HookLoadError(Abort):
    """raised when loading a hook fails, aborting an operation

    Exists to allow more specialized catching."""

class HookAbort(Abort):
    """raised when a validation hook fails, aborting an operation

    Exists to allow more specialized catching."""

class ConfigError(Abort):
    """Exception raised when parsing config files"""

class UpdateAbort(Abort):
    """Raised when an update is aborted for destination issue"""

class MergeDestAbort(Abort):
    """Raised when an update is aborted for destination issues"""

class NoMergeDestAbort(MergeDestAbort):
    """Raised when an update is aborted because there is nothing to merge"""

class ManyMergeDestAbort(MergeDestAbort):
    """Raised when an update is aborted because destination is ambigious"""

class ResponseExpected(Abort):
    """Raised when an EOF is received for a prompt"""
    def __init__(self):
        from .i18n import _
        Abort.__init__(self, _('response expected'))

class OutOfBandError(HintException):
    """Exception raised when a remote repo reports failure"""

class ParseError(HintException):
    """Raised when parsing config files and {rev,file}sets (msg[, pos])"""

class UnknownIdentifier(ParseError):
    """Exception raised when a {rev,file}set references an unknown identifier"""

    def __init__(self, function, symbols):
        from .i18n import _
        ParseError.__init__(self, _("unknown identifier: %s") % function)
        self.function = function
        self.symbols = symbols

class RepoError(HintException):
    pass

class RepoLookupError(RepoError):
    pass

class FilteredRepoLookupError(RepoLookupError):
    pass

class CapabilityError(RepoError):
    pass

class RequirementError(RepoError):
    """Exception raised if .hg/requires has an unknown entry."""

class UnsupportedMergeRecords(Abort):
    def __init__(self, recordtypes):
        from .i18n import _
        self.recordtypes = sorted(recordtypes)
        s = ' '.join(self.recordtypes)
        Abort.__init__(
            self, _('unsupported merge state records: %s') % s,
            hint=_('see https://mercurial-scm.org/wiki/MergeStateRecords for '
                   'more information'))

class LockError(IOError):
    def __init__(self, errno, strerror, filename, desc):
        IOError.__init__(self, errno, strerror, filename)
        self.desc = desc

class LockHeld(LockError):
    def __init__(self, errno, filename, desc, locker):
        LockError.__init__(self, errno, 'Lock held', filename, desc)
        self.locker = locker

class LockUnavailable(LockError):
    pass

# LockError is for errors while acquiring the lock -- this is unrelated
class LockInheritanceContractViolation(RuntimeError):
    pass

class ResponseError(Exception):
    """Raised to print an error with part of output and exit."""

class UnknownCommand(Exception):
    """Exception raised if command is not in the command table."""

class AmbiguousCommand(Exception):
    """Exception raised if command shortcut matches more than one command."""

# derived from KeyboardInterrupt to simplify some breakout code
class SignalInterrupt(KeyboardInterrupt):
    """Exception raised on SIGTERM and SIGHUP."""

class SignatureError(Exception):
    pass

class PushRaced(RuntimeError):
    """An exception raised during unbundling that indicate a push race"""

# bundle2 related errors
class BundleValueError(ValueError):
    """error raised when bundle2 cannot be processed"""

class BundleUnknownFeatureError(BundleValueError):
    def __init__(self, parttype=None, params=(), values=()):
        self.parttype = parttype
        self.params = params
        self.values = values
        if self.parttype is None:
            msg = 'Stream Parameter'
        else:
            msg = parttype
        entries = self.params
        if self.params and self.values:
            assert len(self.params) == len(self.values)
            entries = []
            for idx, par in enumerate(self.params):
                val = self.values[idx]
                if val is None:
                    entries.append(val)
                else:
                    entries.append("%s=%r" % (par, val))
        if entries:
            msg = '%s - %s' % (msg, ', '.join(entries))
        ValueError.__init__(self, msg)

class ReadOnlyPartError(RuntimeError):
    """error raised when code tries to alter a part being generated"""

class PushkeyFailed(Abort):
    """error raised when a pushkey part failed to update a value"""

    def __init__(self, partid, namespace=None, key=None, new=None, old=None,
                 ret=None):
        self.partid = partid
        self.namespace = namespace
        self.key = key
        self.new = new
        self.old = old
        self.ret = ret
        # no i18n expected to be processed into a better message
        Abort.__init__(self, 'failed to update value for "%s/%s"'
                       % (namespace, key))

class CensoredNodeError(RevlogError):
    """error raised when content verification fails on a censored node

    Also contains the tombstone data substituted for the uncensored data.
    """

    def __init__(self, filename, node, tombstone):
        from .node import short
        RevlogError.__init__(self, '%s:%s' % (filename, short(node)))
        self.tombstone = tombstone

class CensoredBaseError(RevlogError):
    """error raised when a delta is rejected because its base is censored

    A delta based on a censored revision must be formed as single patch
    operation which replaces the entire base with new content. This ensures
    the delta may be applied by clones which have not censored the base.
    """

class InvalidBundleSpecification(Exception):
    """error raised when a bundle specification is invalid.

    This is used for syntax errors as opposed to support errors.
    """

class UnsupportedBundleSpecification(Exception):
    """error raised when a bundle specification is not supported."""