Optimized BugDir.uuids, caching on-disk bug uuids.

Output of
  python -m cProfile -o profile be list
  python -c "import pstats; p=pstats.Stats('profile'); p.sort_stats('cumulative').print_stats()"
on my slow netbook before optimization:
   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
    10290    0.417    0.000   10.832    0.001 libbe/bugdir.py:237(uuids)
after optimization:
      105    0.063    0.001    0.250    0.002 libbe/bugdir.py:237(uuids)
The old generator produced many more calls than the new
implementation, but the number of calls was not the source of the
slowdown (data not shown ;).

1 files changed, 10 insertions, 13 deletions

diff --git a/libbe/bugdir.py b/libbe/bugdir.py
index 5967a7e..4711a8f 100644
--- a/libbe/bugdir.py
+++ b/libbe/bugdir.py
@@ -234,19 +234,16 @@ class BugDir (list, settings_object.SavedSettingsObject):
 
     # methods for managing bugs
 
-    def uuids(self):
-        uuids = []
-        # list the uuids in memory
-        for bug in self:
-            uuids.append(bug.uuid)
-            yield bug.uuid
-        if self.storage != None and self.storage.is_readable():
-            # and the ones that are still just in storage
-            child_uuids = libbe.util.id.child_uuids(
-                self.storage.children(self.id.storage()))
-            for id in child_uuids:
-                if id not in uuids:
-                    yield id
+    def uuids(self, use_cached_disk_uuids=True):
+        if use_cached_disk_uuids==False or not hasattr(self, '_uuids_cache'):
+            self._uuids_cache = []
+            # list bugs that are in storage
+            if self.storage != None and self.storage.is_readable():
+                child_uuids = libbe.util.id.child_uuids(
+                    self.storage.children(self.id.storage()))
+                for id in child_uuids:
+                    self._uuids_cache.append(id)
+        return list(set([bug.uuid for bug in self] + self._uuids_cache))
 
     def _clear_bugs(self):
         while len(self) > 0: