From 337fec14957b98c01bc61a5b516bcf8cd98ccb82 Mon Sep 17 00:00:00 2001 From: Martin Pitt Date: Fri, 25 Jun 2010 16:10:13 +0200 Subject: apt/cache.py: When iterating over the cache, do so sorted by package name. With this we read the the package lists linearly if we need to access the package records, instead of having to do thousands of random seeks; the latter is disastrous if we use compressed package indexes, and slower than necessary for uncompressed indexes. --- apt/cache.py | 12 +++++++++++- debian/changelog | 5 +++++ 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/apt/cache.py b/apt/cache.py index 8e07e4d0..3679e4ba 100644 --- a/apt/cache.py +++ b/apt/cache.py @@ -64,6 +64,7 @@ class Cache(object): self._callbacks = {} self._weakref = weakref.WeakValueDictionary() self._set = set() + self._sorted_set = None if memonly: # force apt to build its caches in memory apt_pkg.config.set("Dir::Cache::pkgcache", "") @@ -126,6 +127,7 @@ class Cache(object): self._list = apt_pkg.SourceList() self._list.read_main_list() self._set.clear() + self._sorted_set = None self._weakref.clear() progress.op = _("Building data structures") @@ -157,7 +159,15 @@ class Cache(object): raise KeyError('The cache has no package named %r' % key) def __iter__(self): - for pkgname in self._set: + # We iterate sorted over package names here. With this we read the + # package lists linearly if we need to access the package records, + # instead of having to do thousands of random seeks; the latter + # is disastrous if we use compressed package indexes, and slower than + # necessary for uncompressed indexes. + if self._sorted_set is None: + self._sorted_set = sorted(self._set) + + for pkgname in self._sorted_set: yield self[pkgname] raise StopIteration diff --git a/debian/changelog b/debian/changelog index ae9f5689..b7bb3ad0 100644 --- a/debian/changelog +++ b/debian/changelog @@ -18,6 +18,11 @@ python-apt (0.7.96) UNRELEASED; urgency=low also that accessing it does not take an inordinate amount of time. This exposes a severe performance problem when using gzip compressed package indexes. + * apt/cache.py: When iterating over the cache, do so sorted by package name. + With this we read the the package lists linearly if we need to access the + package records, instead of having to do thousands of random seeks; the + latter is disastrous if we use compressed package indexes, and slower than + necessary for uncompressed indexes. -- Michael Vogt Tue, 01 Jun 2010 16:20:00 +0200 -- cgit v1.2.3