2 files changed, 31 insertions, 4 deletions
diff --git a/synapse/storage/engines/sqlite.py b/synapse/storage/engines/sqlite.py
index c64d73ff21..31b8449ca1 100644
--- a/synapse/storage/engines/sqlite.py
+++ b/synapse/storage/engines/sqlite.py
@@ -15,7 +15,6 @@
 
 import struct
 import threading
-from sqlite3 import sqlite_version_info
 
 from synapse.storage.prepare_database import prepare_database
 
@@ -34,10 +33,14 @@ class Sqlite3Engine(object):
     @property
     def can_native_upsert(self):
         """
-        Do we support native UPSERTs? This requires SQLite3 3.24+, plus some
-        more work we haven't done yet to tell what was inserted vs updated.
+        Do we support native UPSERTs?
         """
-        return sqlite_version_info >= (3, 24, 0)
+        # SQLite3 3.24+ supports them, but empirically the unit tests don't work
+        # when its enabled.
+        # FIXME: Figure out what is wrong so we can re-enable native upserts
+
+        # return self.module.sqlite_version_info >= (3, 24, 0)
+        return False
 
     def check_database(self, txn):
         pass
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index a134e9b3e8..c3ab7db7ae 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -437,6 +437,30 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
         create_event = yield self.get_event(create_id)
         defer.returnValue(create_event.content.get("room_version", "1"))
 
+    @defer.inlineCallbacks
+    def get_room_predecessor(self, room_id):
+        """Get the predecessor room of an upgraded room if one exists.
+        Otherwise return None.
+
+        Args:
+            room_id (str)
+
+        Returns:
+            Deferred[unicode|None]: predecessor room id
+        """
+        state_ids = yield self.get_current_state_ids(room_id)
+        create_id = state_ids.get((EventTypes.Create, ""))
+
+        # If we can't find the create event, assume we've hit a dead end
+        if not create_id:
+            defer.returnValue(None)
+
+        # Retrieve the room's create event
+        create_event = yield self.get_event(create_id)
+
+        # Return predecessor if present
+        defer.returnValue(create_event.content.get("predecessor", None))
+
     @cached(max_entries=100000, iterable=True)
     def get_current_state_ids(self, room_id):
         """Get the current state event ids for a room based on the