2 files changed, 21 insertions, 11 deletions
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index db01eb6d14..0039c281cd 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -442,14 +442,9 @@ class EventsStore(SQLBaseStore):
         else:
             return
 
-        existing_state_rows = yield self._simple_select_list(
-            table="current_state_events",
-            keyvalues={"room_id": room_id},
-            retcols=["event_id", "type", "state_key"],
-            desc="_calculate_state_delta",
-        )
+        existing_state = yield self.get_current_state_ids(room_id)
 
-        existing_events = set(row["event_id"] for row in existing_state_rows)
+        existing_events = set(existing_state.itervalues())
         new_events = set(ev_id for ev_id in current_state.itervalues())
         changed_events = existing_events ^ new_events
 
@@ -457,9 +452,8 @@ class EventsStore(SQLBaseStore):
             return
 
         to_delete = {
-            (row["type"], row["state_key"]): row["event_id"]
-            for row in existing_state_rows
-            if row["event_id"] in changed_events
+            key: ev_id for key, ev_id in existing_state.iteritems()
+            if ev_id in changed_events
         }
         events_to_insert = (new_events - existing_events)
         to_insert = {
@@ -585,6 +579,10 @@ class EventsStore(SQLBaseStore):
                     txn, self.get_users_in_room, (room_id,)
                 )
 
+                self._invalidate_cache_and_stream(
+                    txn, self.get_current_state_ids, (room_id,)
+                )
+
         for room_id, new_extrem in new_forward_extremeties.items():
             self._simple_delete_txn(
                 txn,
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index 84482d8285..27f1ec89ec 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -14,7 +14,7 @@
 # limitations under the License.
 
 from ._base import SQLBaseStore
-from synapse.util.caches.descriptors import cached, cachedList
+from synapse.util.caches.descriptors import cached, cachedList, cachedInlineCallbacks
 from synapse.util.caches import intern_string
 from synapse.storage.engines import PostgresEngine
 
@@ -69,6 +69,18 @@ class StateStore(SQLBaseStore):
             where_clause="type='m.room.member'",
         )
 
+    @cachedInlineCallbacks(max_entries=100000, iterable=True)
+    def get_current_state_ids(self, room_id):
+        rows = yield self._simple_select_list(
+            table="current_state_events",
+            keyvalues={"room_id": room_id},
+            retcols=["event_id", "type", "state_key"],
+            desc="_calculate_state_delta",
+        )
+        defer.returnValue({
+            (r["type"], r["state_key"]): r["event_id"] for r in rows
+        })
+
     @defer.inlineCallbacks
     def get_state_groups_ids(self, room_id, event_ids):
         if not event_ids: