1 files changed, 16 insertions, 5 deletions
diff --git a/synapse/util/caches/stream_change_cache.py b/synapse/util/caches/stream_change_cache.py
index 70fe00ce0b..941d873ab8 100644
--- a/synapse/util/caches/stream_change_cache.py
+++ b/synapse/util/caches/stream_change_cache.py
@@ -13,20 +13,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.util.caches import register_cache
+from synapse.util.caches import register_cache, CACHE_SIZE_FACTOR
 
 
 from blist import sorteddict
 import logging
-import os
 
 
 logger = logging.getLogger(__name__)
 
 
-CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))
-
-
 class StreamChangeCache(object):
     """Keeps track of the stream positions of the latest change in a set of entities.
 
@@ -89,6 +85,21 @@ class StreamChangeCache(object):
 
         return result
 
+    def has_any_entity_changed(self, stream_pos):
+        """Returns if any entity has changed
+        """
+        assert type(stream_pos) is int
+
+        if stream_pos >= self._earliest_known_stream_pos:
+            self.metrics.inc_hits()
+            keys = self._cache.keys()
+            i = keys.bisect_right(stream_pos)
+
+            return i < len(keys)
+        else:
+            self.metrics.inc_misses()
+            return True
+
     def get_all_entities_changed(self, stream_pos):
         """Returns all entites that have had new things since the given
         position. If the position is too old it will return None.