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400 lines
15 KiB
400 lines
15 KiB
# -*- coding: utf-8 -*-
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# Copyright (C) 2012 Niels Thykier <niels@thykier.net>
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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from collections import defaultdict
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from contextlib import contextmanager
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from britney2.utils import ifilter_except, iter_except
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from britney2.installability.solver import InstallabilitySolver
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class _RelationBuilder(object):
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"""Private helper class to "build" relations"""
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def __init__(self, itbuilder, binary):
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self._itbuilder = itbuilder
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self._binary = binary
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binary_data = itbuilder._package_table[binary]
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self._new_deps = set(binary_data[0])
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self._new_breaks = set(binary_data[1])
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def add_dependency_clause(self, or_clause):
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"""Add a dependency clause
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The clause must be a sequence of (name, version, architecture)
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tuples. The clause is an OR clause, i.e. any tuple in the
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sequence can satisfy the relation. It is irrelevant if the
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dependency is from the "Depends" or the "Pre-Depends" field.
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Note that is the sequence is empty, the dependency is assumed
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to be unsatisfiable.
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The binaries in the clause are not required to have been added
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to the InstallabilityTesterBuilder when this method is called.
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However, they must be added before the "build()" method is
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called.
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"""
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itbuilder = self._itbuilder
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clause = itbuilder._intern_set(or_clause)
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binary = self._binary
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okay = False
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for dep_tuple in clause:
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okay = True
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rdeps, _, rdep_relations = itbuilder._reverse_relations(dep_tuple)
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rdeps.add(binary)
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rdep_relations.add(clause)
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self._new_deps.add(clause)
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if not okay:
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itbuilder._broken.add(binary)
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def add_breaks(self, broken_binary):
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"""Add a Breaks-clause
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Marks the given binary as being broken by the current
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package. That is, the given package satisfies a relation
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in either the "Breaks" or the "Conflicts" field. The binary
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given must be a (name, version, architecture)-tuple.
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The binary is not required to have been added to the
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InstallabilityTesterBuilder when this method is called. However,
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it must be added before the "build()" method is called.
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"""
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itbuilder = self._itbuilder
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self._new_breaks.add(broken_binary)
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reverse_relations = itbuilder._reverse_relations(broken_binary)
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reverse_relations[1].add(self._binary)
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def _commit(self):
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itbuilder = self._itbuilder
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data = (itbuilder._intern_set(self._new_deps),
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itbuilder._intern_set(self._new_breaks))
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itbuilder._package_table[self._binary] = data
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class InstallabilityTesterBuilder(object):
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"""Builder to create instances of InstallabilityTester"""
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def __init__(self):
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self._package_table = {}
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self._reverse_package_table = {}
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self._essentials = set()
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self._testing = set()
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self._internmap = {}
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self._broken = set()
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def add_binary(self, binary, essential=False, in_testing=False,
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frozenset=frozenset):
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"""Add a new binary package
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Adds a new binary package. The binary must be given as a
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(name, version, architecture)-tuple. Returns True if this
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binary is new (i.e. has never been added before) or False
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otherwise.
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Keyword arguments:
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* essential - Whether this package is "Essential: yes".
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* in_testing - Whether this package is in testing.
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The frozenset argument is a private optimisation.
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Cave-at: arch:all packages should be "re-mapped" to given
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architecture. That is, (pkg, version, "all") should be
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added as:
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for arch in architectures:
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binary = (pkg, version, arch)
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it.add_binary(binary)
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The resulting InstallabilityTester relies on this for
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correctness!
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"""
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# Note, even with a dup, we need to do these
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if in_testing:
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self._testing.add(binary)
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if essential:
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self._essentials.add(binary)
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if binary not in self._package_table:
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# Allow binaries to be added multiple times (happens
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# when sid and testing have the same version)
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self._package_table[binary] = (frozenset(), frozenset())
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return True
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return False
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@contextmanager
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def relation_builder(self, binary):
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"""Returns a _RelationBuilder for a given binary [context]
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This method returns a context-managed _RelationBuilder for a
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given binary. So it should be used in a "with"-statment,
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like:
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with it.relation_builder(binary) as rel:
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rel.add_dependency_clause(dependency_clause)
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rel.add_breaks(pkgtuple)
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...
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The binary given must be a (name, version, architecture)-tuple.
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Note, this method is optimised to be called at most once per
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binary.
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"""
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if binary not in self._package_table:
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raise ValueError("Binary %s/%s/%s does not exist" % binary)
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rel = _RelationBuilder(self, binary)
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yield rel
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rel._commit()
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def _intern_set(self, s, frozenset=frozenset):
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"""Freeze and intern a given sequence (set variant of intern())
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Given a sequence, create a frozenset copy (if it is not
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already a frozenset) and intern that frozen set. Returns the
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interned set.
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At first glance, interning sets may seem absurd. However,
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it does enable memory savings of up to 600MB when applied
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to the "inner" sets of the dependency clauses and all the
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conflicts relations as well.
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"""
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if type(s) == frozenset:
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fset = s
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else:
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fset = frozenset(s)
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if fset in self._internmap:
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return self._internmap[fset]
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self._internmap[fset] = fset
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return fset
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def _reverse_relations(self, binary, set=set):
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"""Return the reverse relations for a binary
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Fetch the reverse relations for a given binary, which are
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created lazily.
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"""
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if binary in self._reverse_package_table:
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return self._reverse_package_table[binary]
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rel = [set(), set(), set()]
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self._reverse_package_table[binary] = rel
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return rel
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def build(self):
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"""Compile the installability tester
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This method will compile an installability tester from the
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information given and (where possible) try to optimise a
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few things.
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"""
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package_table = self._package_table
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reverse_package_table = self._reverse_package_table
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intern_set = self._intern_set
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safe_set = set()
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broken = self._broken
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not_broken = ifilter_except(broken)
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check = set(broken)
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def safe_set_satisfies(t):
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"""Check if t's dependencies can be satisfied by the safe set"""
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if not package_table[t][0]:
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# If it has no dependencies at all, then it is safe. :)
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return True
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for depgroup in package_table[t][0]:
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if not any(dep for dep in depgroup if dep in safe_set):
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return False
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return True
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# Merge reverse conflicts with conflicts - this saves some
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# operations in _check_loop since we only have to check one
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# set (instead of two) and we remove a few duplicates here
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# and there.
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#
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# At the same time, intern the rdep sets
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for pkg in reverse_package_table:
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if pkg not in package_table:
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raise RuntimeError("%s/%s/%s referenced but not added!" % pkg)
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deps, con = package_table[pkg]
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rdeps, rcon, rdep_relations = reverse_package_table[pkg]
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if rcon:
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if not con:
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con = intern_set(rcon)
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else:
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con = intern_set(con | rcon)
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package_table[pkg] = (deps, con)
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reverse_package_table[pkg] = (intern_set(rdeps), con,
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intern_set(rdep_relations))
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# Check if we can expand broken.
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for t in not_broken(iter_except(check.pop, KeyError)):
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# This package is not known to be broken... but it might be now
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isb = False
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for depgroup in package_table[t][0]:
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if not any(not_broken(depgroup)):
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# A single clause is unsatisfiable, the
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# package can never be installed - add it to
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# broken.
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isb = True
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break
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if not isb:
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continue
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broken.add(t)
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if t not in reverse_package_table:
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continue
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check.update(reverse_package_table[t][0] - broken)
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if broken:
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# Since a broken package will never be installable, nothing that depends on it
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# will ever be installable. Thus, there is no point in keeping relations on
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# the broken package.
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seen = set()
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empty_set = frozenset()
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null_data = (frozenset([empty_set]), empty_set)
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for b in (x for x in broken if x in reverse_package_table):
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for rdep in (r for r in not_broken(reverse_package_table[b][0])
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if r not in seen):
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ndep = intern_set((x - broken) for x in package_table[rdep][0])
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package_table[rdep] = (ndep, package_table[rdep][1] - broken)
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seen.add(rdep)
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# Since they won't affect the installability of any other package, we might as
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# as well null their data. This memory for these packages, but likely there
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# will only be a handful of these "at best" (fsvo of "best")
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for b in broken:
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package_table[b] = null_data
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if b in reverse_package_table:
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del reverse_package_table[b]
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# Now find an initial safe set (if any)
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check = set()
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for pkg in package_table:
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if package_table[pkg][1]:
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# has (reverse) conflicts - not safe
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continue
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if not safe_set_satisfies(pkg):
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continue
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safe_set.add(pkg)
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if pkg in reverse_package_table:
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# add all rdeps (except those already in the safe_set)
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check.update(reverse_package_table[pkg][0] - safe_set)
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# Check if we can expand the initial safe set
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for pkg in iter_except(check.pop, KeyError):
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if package_table[pkg][1]:
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# has (reverse) conflicts - not safe
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continue
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if safe_set_satisfies(pkg):
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safe_set.add(pkg)
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if pkg in reverse_package_table:
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# add all rdeps (except those already in the safe_set)
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check.update(reverse_package_table[pkg][0] - safe_set)
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eqv_table = self._build_eqv_packages_table(package_table,
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reverse_package_table)
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return InstallabilitySolver(package_table,
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reverse_package_table,
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self._testing, self._broken,
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self._essentials, safe_set,
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eqv_table)
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def _build_eqv_packages_table(self, package_table,
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reverse_package_table,
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frozenset=frozenset):
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"""Attempt to build a table of equivalent packages
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This method attempts to create a table of packages that are
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equivalent (in terms of installability). If two packages (A
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and B) are equivalent then testing the installability of A is
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the same as testing the installability of B. This equivalency
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also applies to co-installability.
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The example cases:
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* aspell-*
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* ispell-*
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Cases that do *not* apply:
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* MTA's
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The theory:
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The packages A and B are equivalent iff:
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reverse_depends(A) == reverse_depends(B) AND
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conflicts(A) == conflicts(B) AND
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depends(A) == depends(B)
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Where "reverse_depends(X)" is the set of reverse dependencies
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of X, "conflicts(X)" is the set of negative dependencies of X
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(Breaks and Conflicts plus the reverse ones of those combined)
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and "depends(X)" is the set of strong dependencies of X
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(Depends and Pre-Depends combined).
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To be honest, we are actually equally interested another
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property as well, namely substitutability. The package A can
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always used instead of B, iff:
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reverse_depends(A) >= reverse_depends(B) AND
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conflicts(A) <= conflicts(B) AND
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depends(A) == depends(B)
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(With the same definitions as above). Note that equivalency
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is just a special-case of substitutability, where A and B can
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substitute each other (i.e. a two-way substituation).
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Finally, note that the "depends(A) == depends(B)" for
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substitutability is actually not a strict requirement. There
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are cases where those sets are different without affecting the
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property.
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"""
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# Despite talking about substitutability, the method currently
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# only finds the equivalence cases. Lets leave
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# substitutability for a future version.
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find_eqv_table = defaultdict(list)
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eqv_table = {}
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for pkg in reverse_package_table:
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rdeps = reverse_package_table[pkg][2]
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if not rdeps:
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# we don't care for things without rdeps (because
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# it is not worth it)
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continue
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deps, con = package_table[pkg]
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ekey = (deps, con, rdeps)
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find_eqv_table[ekey].append(pkg)
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for pkg_list in find_eqv_table.values():
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if len(pkg_list) < 2:
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continue
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eqv_set = frozenset(pkg_list)
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for pkg in pkg_list:
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eqv_table[pkg] = eqv_set
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return eqv_table
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