db/manager: Drop async method

As far as I can tell using a separate process doesn't actually improve
performance, it makes it worse. The work that we're passing off to the
separate function isn't necessarily work that's well suited to being
handed off, there isn't a lot of computation and the objects that need
to be passed across the pipe are fairly large (at least when considering
a pipe). Converting the function to a generator gives better performance
and simplifies the implementation.

1 files changed, 15 insertions, 31 deletions

diff --git a/alot/buffers/search.py b/alot/buffers/search.py
index c5b6bbcd..8cd76a87 100644
--- a/alot/buffers/search.py
+++ b/alot/buffers/search.py
@@ -8,16 +8,16 @@ from .buffer import Buffer
 from ..settings.const import settings
 from ..widgets.search import ThreadlineWidget
 
-class PipeWalker(urwid.ListWalker):
+class IterWalker(urwid.ListWalker):
     """
-    urwid.ListWalker that reads next items from a pipe and wraps them in
+    urwid.ListWalker that reads next items from a generator and wraps them in
     ThreadlineWidget widgets for displaying
     """
 
     _pipe  = None
     _dbman = None
 
-    _pipe_eof = False
+    _iter_done = False
 
     # list of the thread IDs
     _tids  = None
@@ -26,9 +26,9 @@ class PipeWalker(urwid.ListWalker):
 
     _focus = None
 
-    def __init__(self, pipe, dbman):
-        self._pipe  = pipe
-        self._dbman = dbman
+    def __init__(self, threads, dbman):
+        self._threads = threads
+        self._dbman   = dbman
 
         self._tids = []
         self._wgts = {}
@@ -38,7 +38,7 @@ class PipeWalker(urwid.ListWalker):
         super().__init__()
 
     def __len__(self):
-        while not self._pipe_eof:
+        while not self._iter_done:
             self._get_next_item()
         return len(self._tids)
 
@@ -58,7 +58,7 @@ class PipeWalker(urwid.ListWalker):
         if pos < 0:
             raise IndexError
 
-        while not self._pipe_eof and pos >= len(self._tids):
+        while not self._iter_done and pos >= len(self._tids):
             self._get_next_item()
 
         if pos >= len(self._tids):
@@ -80,13 +80,13 @@ class PipeWalker(urwid.ListWalker):
         self._modified()
 
     def _get_next_item(self):
-        if self._pipe_eof:
+        if self._iter_done:
             return None
 
         try:
-            self._tids.append(self._pipe.recv())
-        except EOFError:
-            self._pipe_eof = True
+            self._tids.append(next(self._threads))
+        except StopIteration:
+            self._iter_done = True
 
 class SearchBuffer(Buffer):
     """shows a result list of threads for a query"""
@@ -102,7 +102,6 @@ class SearchBuffer(Buffer):
         self.querystring = initialquery
         default_order = settings.get('search_threads_sort_order')
         self.sort_order = sort_order or default_order
-        self.proc = None  # process that fills our pipe
         self.rebuild()
 
         super().__init__()
@@ -132,21 +131,7 @@ class SearchBuffer(Buffer):
         info['result_count_positive'] = 's' if info['result_count'] > 1 else ''
         return info
 
-    def cleanup(self):
-        self.kill_filler_process()
-
-    def kill_filler_process(self):
-        """
-        terminates the process that fills this buffers
-        :class:`~alot.walker.PipeWalker`.
-        """
-        if self.proc:
-            if self.proc.is_alive():
-                self.proc.terminate()
-
     def rebuild(self):
-        self.kill_filler_process()
-
         exclude_tags = settings.get_notmuch_setting('search', 'exclude_tags')
         if exclude_tags:
             exclude_tags = frozenset([t for t in exclude_tags.split(';') if t])
@@ -157,9 +142,8 @@ class SearchBuffer(Buffer):
         self._thread_count_val = None
 
         try:
-            self.pipe, self.proc = self.dbman.get_threads(self.querystring,
-                                                          self.sort_order,
-                                                          exclude_tags)
+            threads = self.dbman.get_threads(self.querystring, self.sort_order,
+                                             exclude_tags)
         except NotmuchError:
             self.ui.notify('malformed query string: %s' % self.querystring,
                            'error')
@@ -167,7 +151,7 @@ class SearchBuffer(Buffer):
             self.body = self.listbox
             return
 
-        self.threadlist = PipeWalker(self.pipe, self.dbman)
+        self.threadlist = IterWalker(threads, self.dbman)
 
         self.listbox = urwid.ListBox(self.threadlist)
         self.body = self.listbox