1 files changed, 21 insertions, 0 deletions
diff --git a/synapse/events/snapshot.py b/synapse/events/snapshot.py
index e895b1c450..11605b34a3 100644
--- a/synapse/events/snapshot.py
+++ b/synapse/events/snapshot.py
@@ -15,9 +15,30 @@
 
 
 class EventContext(object):
+    __slots__ = [
+        "current_state_ids",
+        "prev_state_ids",
+        "state_group",
+        "rejected",
+        "push_actions",
+        "prev_group",
+        "delta_ids",
+        "prev_state_events",
+    ]
+
     def __init__(self):
+        # The current state including the current event
         self.current_state_ids = None
+        # The current state excluding the current event
         self.prev_state_ids = None
         self.state_group = None
+
         self.rejected = False
         self.push_actions = []
+
+        # A previously persisted state group and a delta between that
+        # and this state.
+        self.prev_group = None
+        self.delta_ids = None
+
+        self.prev_state_events = None