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[Mikkel Kamstrup Erlandsen <mikkel.kamstrup@xxxxxxxxx>]

Mikkel Kamstrup Erlandsen has proposed merging lp:~zeitgeist/zeitgeist/small-find-events-optimization into lp:zeitgeist.

Requested reviews:
  Zeitgeist Framework Team (zeitgeist)


I was seeing query response times of around 200ms when calling ZG from Unity. As this seems like a  suspiciously long query time for my small database I went looking a bit into this.

First I noticed that the debug/profiling statements we had for this was not only imprecise but also directly hiding the truth. So I fixed that. The problem being that we never really logged the time it took to execute the query where we find, group, and sort the events, only the time it takes us to build the event objects after the query ...

Next thing I noticed was that we spend surprisingly long time in _find_events() when looking up full events compared to just looking up the ids. So I made that function always just find the ids and then do another SQL call to look up the full event structures. Surprisingly adding this extra SQL call shaves off roughly 50ms on the full query time.

(Note: This was done in my Canonical time - so if you accept this branch Zeitgeist will forever be "tainted" bwahaha! ;-P)

-- 
https://code.launchpad.net/~zeitgeist/zeitgeist/small-find-events-optimization/+merge/34065
Your team Zeitgeist Framework Team is requested to review the proposed merge of lp:~zeitgeist/zeitgeist/small-find-events-optimization into lp:zeitgeist.

=== modified file '_zeitgeist/engine/main.py'
--- _zeitgeist/engine/main.py	2010-08-02 10:13:12 +0000
+++ _zeitgeist/engine/main.py	2010-08-30 13:27:45 +0000
@@ -337,7 +337,7 @@
 		if return_mode == 0:
 			sql = "SELECT DISTINCT id FROM event_view"
 		elif return_mode == 1:
-			sql = "SELECT * FROM event_view"
+			sql = "SELECT id FROM event_view"
 		elif return_mode == 2:
 			sql = "SELECT subj_uri, timestamp FROM event_view"
 		else:
@@ -374,14 +374,19 @@
 		
 		result = self._cursor.execute(sql, where.arguments).fetchall()
 		
-		if return_mode == 1:
-			return self.get_events(rows=result, sender=sender)
-		if return_mode == 2:
-			return map(lambda row: (row[0], row[1]), result)
-		else: # return_mode == 0
+		if return_mode == 0:
+			log.debug("Found %d event IDs in %fs" % (len(result), time.time()- t))
 			result = [row[0] for row in result]
-			log.debug("Fetched %d event IDs in %fs" % (len(result), time.time()- t))
-			return result
+		elif return_mode == 1:
+			log.debug("Found %d events in %fs" % (len(result), time.time()- t))
+			result = self.get_events(ids=[row[0] for row in result], sender=sender)			
+		elif return_mode == 2:
+			log.debug("Found %d (uri,timestamp) tuples in %fs" % (len(result), time.time()- t))
+			result = map(lambda row: (row[0], row[1]), result)			
+		else:
+			raise Exception("%d" % return_mode)
+		
+		return result
 	
 	def find_eventids(self, *args):
 		return self._find_events(0, *args)