User Cursor.__iter__ instead of fetchall

This prevents unnecessary construction of lists

1 files changed, 3 insertions, 4 deletions

diff --git a/synapse/storage/devices.py b/synapse/storage/devices.py
index e545b62e39..6beeff8b00 100644
--- a/synapse/storage/devices.py
+++ b/synapse/storage/devices.py
@@ -333,13 +333,12 @@ class DeviceStore(SQLBaseStore):
         txn.execute(
             sql, (destination, from_stream_id, now_stream_id, False)
         )
-        rows = txn.fetchall()
 
-        if not rows:
+        # maps (user_id, device_id) -> stream_id
+        query_map = {(r[0], r[1]): r[2] for r in txn}
+        if not query_map:
             return (now_stream_id, [])
 
-        # maps (user_id, device_id) -> stream_id
-        query_map = {(r[0], r[1]): r[2] for r in rows}
         devices = self._get_e2e_device_keys_txn(
             txn, query_map.keys(), include_all_devices=True
         )