Drop caches after having processed folders.

This enhances a lot memory consumption when you have many folders
to process.

Signed-off-by: Giovanni Mascellani <mascellani@poisson.phc.unipi.it>

offlineimap/accounts.py

@@ -491,3 +491,7 @@ def syncfolder(account, remotefolder, quick):
         ui.error(e, msg = "ERROR in syncfolder for %s folder %s: %s" % \
                 (account, remotefolder.getvisiblename(),
                  traceback.format_exc()))
+    finally:
+        for folder in ["statusfolder", "localfolder", "remotefolder"]:
+            if folder in locals():
+                locals()[folder].dropmessagelistcache()

offlineimap/folder/Base.py

@@ -247,6 +247,9 @@ class BaseFolder(object):
 
         raise NotImplementedError
 
+    def dropmessagelistcache(self):
+        raise NotImplementedException
+
     def getmessagelist(self):
         """Gets the current message list.
         You must call cachemessagelist() before calling this function!"""

offlineimap/folder/IMAP.py

@@ -250,6 +250,8 @@ class IMAPFolder(BaseFolder):
                 rtime = imaplibutil.Internaldate2epoch(messagestr)
                 self.messagelist[uid] = {'uid': uid, 'flags': flags, 'time': rtime}
 
+    def dropmessagelistcache(self):
+        self.messagelist = None
 
     # Interface from BaseFolder
     def getmessagelist(self):

offlineimap/folder/LocalStatus.py

@@ -161,6 +161,8 @@ class LocalStatusFolder(BaseFolder):
         self.readstatus(file)
         file.close()
 
+    def dropmessagelistcache(self):
+        self.messagelist = None
 
     def save(self):
         """Save changed data to disk. For this backend it is the same as saveall."""

offlineimap/folder/LocalStatusSQLite.py

@@ -203,6 +203,9 @@ class LocalStatusSQLiteFolder(BaseFolder):
             self.messagelist[uid]['labels'] = labels
             self.messagelist[uid]['mtime'] = row[2]
 
+    def dropmessagelistcache(self):
+        self.messagelist = None
+
     # Interface from LocalStatusFolder
     def save(self):
         pass

offlineimap/folder/Maildir.py

@@ -220,6 +220,9 @@ class MaildirFolder(BaseFolder):
         if self.messagelist is None:
             self.messagelist = self._scanfolder()
 
+    def dropmessagelistcache(self):
+        self.messagelist = None
+
     # Interface from BaseFolder
     def getmessagelist(self):
         return self.messagelist

offlineimap/folder/UIDMaps.py

@@ -125,6 +125,9 @@ class MappedIMAPFolder(IMAPFolder):
         finally:
             self.maplock.release()
 
+    def dropmessagelistcache(self):
+        self._mb.dropmessagelistcache()
+
     # Interface from BaseFolder
     def uidexists(self, ruid):
         """Checks if the (remote) UID exists in this Folder"""