Don't needlessly compute context

2 files changed, 17 insertions, 4 deletions

diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 46ce3699d7..5503d9ae86 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -900,8 +900,10 @@ class FederationHandler(BaseHandler):
             event.event_id, event.signatures,
         )
 
+        outlier = event.internal_metadata.is_outlier()
+
         context = yield self.state_handler.compute_event_context(
-            event, old_state=state
+            event, old_state=state, outlier=outlier,
         )
 
         if not auth_events:
@@ -912,7 +914,7 @@ class FederationHandler(BaseHandler):
             event.event_id, auth_events,
         )
 
-        is_new_state = not event.internal_metadata.is_outlier()
+        is_new_state = not outlier
 
         # This is a hack to fix some old rooms where the initial join event
         # didn't reference the create event in its auth events.
diff --git a/synapse/state.py b/synapse/state.py
index 9dddb77d5b..c1ce46d1b2 100644
--- a/synapse/state.py
+++ b/synapse/state.py
@@ -106,7 +106,7 @@ class StateHandler(object):
         defer.returnValue(state)
 
     @defer.inlineCallbacks
-    def compute_event_context(self, event, old_state=None):
+    def compute_event_context(self, event, old_state=None, outlier=False):
         """ Fills out the context with the `current state` of the graph. The
         `current state` here is defined to be the state of the event graph
         just before the event - i.e. it never includes `event`
@@ -119,9 +119,20 @@ class StateHandler(object):
         Returns:
             an EventContext
         """
+        yield run_on_reactor()
+
         context = EventContext()
 
-        yield run_on_reactor()
+        if outlier:
+            if old_state:
+                context.current_state = {
+                    (s.type, s.state_key): s for s in old_state
+                }
+            else:
+                context.current_state = {}
+            context.prev_state_events = []
+            context.state_group = None
+            defer.returnValue(context)
 
         if old_state:
             context.current_state = {