apt/cache.py: Make Cache.get_changes() much (~35x) faster (Closes: #578074).

This change consists of the following ideas:
 - Switch to the low-level API
 - Use 'not marked_keep()' to check if a package has
   been modified.

1 files changed, 8 insertions, 4 deletions

diff --git a/apt/cache.py b/apt/cache.py
index cfe6bedc..3b0c5f7e 100644
--- a/apt/cache.py
+++ b/apt/cache.py
@@ -176,10 +176,14 @@ class Cache(object):
     def get_changes(self):
         """ Get the marked changes """
         changes = []
-        for pkg in self:
-            if (pkg.marked_upgrade or pkg.marked_install or pkg.marked_delete
-                or pkg.marked_downgrade or pkg.marked_reinstall):
-                changes.append(pkg)
+        marked_keep = self._depcache.marked_keep
+        for pkg in self._cache.packages:
+            if not marked_keep(pkg):
+                try:
+                    changes.append(self._weakref[pkg.name])
+                except KeyError:
+                    package = self._weakref[pkg.name] = Package(self, pkg)
+                    changes.append(package)
         return changes
 
     @deprecated_args