performance of playlistinfo <id> and status not dependent on playlist length

mopidy/backends/base/current_playlist.py

@@ -1,6 +1,7 @@
 from copy import copy
 import logging
 import random
+import pprint
 
 from mopidy.listeners import BackendListener
 from mopidy.models import CpTrack
@@ -28,6 +29,7 @@ class CurrentPlaylistController(object):
 
         Read-only.
         """
+        logger.debug(u'current_playlist.cp_tracks')
         return [copy(ct) for ct in self._cp_tracks]
 
     @property
@@ -37,8 +39,16 @@ class CurrentPlaylistController(object):
 
         Read-only.
         """
+        logger.debug(u'current_playlist.tracks()')
         return [ct[1] for ct in self._cp_tracks]
 
+    @property
+    def tracks_len(self):
+        """
+        Length of current playlist
+        """
+        return len(self._cp_tracks)
+
     @property
     def version(self):
         """

mopidy/frontends/mpd/protocol/current_playlist.py

@@ -254,6 +254,12 @@ def playlistinfo(context, songpos=None,
         end = songpos + 1
         if start == -1:
             end = None
+        else:
+            #Fetch one single track, hot code path (avoid deep-copying the entire playlist)
+            res = context.backend.current_playlist.get(cpid=songpos).get()
+            cpids = [res.cpid]
+            l = [res.track]
+            return tracks_to_mpd_format(l, 0, 1, cpids=cpids)
         cpids = [ct[0] for ct in
             context.backend.current_playlist.cp_tracks.get()]
         return tracks_to_mpd_format(

mopidy/frontends/mpd/protocol/status.py

@@ -166,7 +166,7 @@ def status(context):
           decimal places for millisecond precision.
     """
     futures = {
-        'current_playlist.tracks': context.backend.current_playlist.tracks,
+        'current_playlist.tracks_len': context.backend.current_playlist.tracks_len,
         'current_playlist.version': context.backend.current_playlist.version,
         'mixer.volume': context.mixer.volume,
         'playback.consume': context.backend.playback.consume,
@@ -213,7 +213,7 @@ def _status_consume(futures):
         return 0
 
 def _status_playlist_length(futures):
-    return len(futures['current_playlist.tracks'].get())
+    return futures['current_playlist.tracks_len'].get()
 
 def _status_playlist_version(futures):
     return futures['current_playlist.version'].get()