db: make sure to close the read-only database instances

2 files changed, 27 insertions, 19 deletions

diff --git a/alot/db/manager.py b/alot/db/manager.py
index ba9271fc..728dcddb 100644
--- a/alot/db/manager.py
+++ b/alot/db/manager.py
@@ -4,6 +4,7 @@
 
 import abc
 import asyncio
+from   contextlib import closing
 import logging
 import os
 
@@ -151,37 +152,41 @@ class DBManager:
         self._property_tags = frozenset(settings.get('property_tags'))
 
     def _db_ro(self):
-        return Database(path = self.path, mode = Database.MODE.READ_ONLY)
+        return closing(Database(path = self.path, mode = Database.MODE.READ_ONLY))
 
 
 
     def count_messages(self, querystring):
         """returns number of messages that match `querystring`"""
-        return self._db_ro().count_messages(querystring, exclude_tags = self._exclude_tags)
+        with self._db_ro() as db:
+            return db.count_messages(querystring, exclude_tags = self._exclude_tags)
 
     def count_threads(self, querystring):
         """returns number of threads that match `querystring`"""
-        return self._db_ro().count_threads(querystring, exclude_tags = self._exclude_tags)
+        with self._db_ro() as db:
+            return db.count_threads(querystring, exclude_tags = self._exclude_tags)
 
-    def _get_notmuch_thread(self, tid):
+    def _get_notmuch_thread(self, db, tid):
         """returns :class:`notmuch.database.Thread` with given id"""
         querystr = 'thread:' + tid
         try:
-            return next(self._db_ro().threads(querystr, exclude_tags = self._exclude_tags))
+            return next(db.threads(querystr, exclude_tags = self._exclude_tags))
         except StopIteration:
             errmsg = 'no thread with id %s exists!' % tid
             raise NonexistantObjectError(errmsg)
 
     def get_thread(self, tid):
         """returns :class:`Thread` with given thread id (str)"""
-        return Thread(self, self._get_notmuch_thread(tid))
+        with self._db_ro() as db:
+            return Thread(self, self._get_notmuch_thread(db, tid))
 
     def get_all_tags(self):
         """
         returns all tagsstrings used in the database
         :rtype: set of str
         """
-        return self._db_ro().tags
+        with self._db_ro() as db:
+            return set(db.tags)
 
     def get_named_queries(self):
         """
@@ -190,9 +195,9 @@ class DBManager:
         """
         q_prefix = 'query.'
 
-        db = self._db_ro()
-        queries = filter(lambda k: k.startswith(q_prefix), db.config)
-        return { q[len(q_prefix):] : db.config[q] for q in queries }
+        with self._db_ro() as db:
+            queries = filter(lambda k: k.startswith(q_prefix), db.config)
+            return { q[len(q_prefix):] : db.config[q] for q in queries }
 
     def get_threads(self, querystring, sort='newest_first', exclude_tags = frozenset()):
         """
@@ -211,11 +216,12 @@ class DBManager:
         # TODO: use a symbolic constant for this
         assert sort in self._sort_orders
 
-        db           = self._db_ro()
-        sort         = self._sort_orders[sort]
-        exclude_tags = self._exclude_tags | exclude_tags
+        with self._db_ro() as db:
+            sort         = self._sort_orders[sort]
+            exclude_tags = self._exclude_tags | exclude_tags
 
-        return (t.threadid for t in db.threads(querystring, sort = sort, exclude_tags = exclude_tags))
+            for t in db.threads(querystring, sort = sort, exclude_tags = exclude_tags):
+                yield t.threadid
 
     async def startup(self):
         self._write_queue = asyncio.Queue()
diff --git a/alot/db/thread.py b/alot/db/thread.py
index 1f9ae7f0..37cc5fc7 100644
--- a/alot/db/thread.py
+++ b/alot/db/thread.py
@@ -61,13 +61,10 @@ class Thread:
         self.message_list      = []
         self.messages          = {}
 
-        self.refresh(thread)
+        self._refresh(thread)
 
-    def refresh(self, thread = None):
+    def _refresh(self, thread):
         """refresh thread metadata from the index"""
-        if not thread:
-            thread = self._dbman._get_notmuch_thread(self.id)
-
         self.total_messages = len(thread)
         self._notmuch_authors_string = thread.authors
 
@@ -97,6 +94,11 @@ class Thread:
 
         self.messages, self.toplevel_messages, self.message_list = self._gather_messages(thread)
 
+    def refresh(self):
+        with self._dbman._db_ro() as db:
+            thread = self._dbman._get_notmuch_thread(db, self.id)
+            self._refresh(thread)
+
     def _gather_messages(self, thread):
         msgs     = {}
         msg_tree = []